DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA 1. Study of OP AMPs - IC 741, IC 555, IC 565, IC 566, IC 1496-functioning, parameters and specifications IC 741 General Description: The IC 741 is a high performance monolithic operational amplifier constructed using the planer epitaxial process. High common mode voltage range and absence of latch-up tendencies make the IC 741 ideal for use as voltage follower. The high gain and wide range of operating voltage provide superior performance in integrator, summing amplifier and general feed back applications. Block Diagram of Op-Amp: Pin Configuration: LINEAR IC APPLICATIONS LABORATORY 1
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
1. Study of OP AMPs - IC 741, IC 555, IC 565, IC 566,
IC 1496-functioning, parameters and specifications
IC 741
General Description:
The IC 741 is a high performance monolithic operational amplifier constructed
using the planer epitaxial process. High common mode voltage range and absence
of latch-up tendencies make the IC 741 ideal for use as voltage follower. The high
gain and wide range of operating voltage provide superior performance in integrator,
summing amplifier and general feed back applications.
Block Diagram of Op-Amp:
Pin Configuration:
LINEAR IC APPLICATIONS LABORATORY 1
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Features:
1. No frequency compensation required.
2. Short circuit protection
3. Offset voltage null capability
4. Large common mode and differential voltage ranges
5. Low power consumption
6. No latch-up
Specifications:
1. Voltage gain A = α typically 2,00,000
2. I/P resistance RL = α Ω, practically 2MΩ
3. O/P resistance R =0, practically 75Ω
4. Bandwidth = α Hz. It can be operated at any frequency
5. Common mode rejection ratio = α
(Ability of op amp to reject noise voltage)
6. Slew rate + α V/μsec
(Rate of change of O/P voltage)
7. When V1 = V2, VD=0
8. Input offset voltage (Rs ≤ 10KΩ) max 6 mv
9. Input offset current = max 200nA
10. Input bias current : 500nA
11. Input capacitance : typical value 1.4pF
12. Offset voltage adjustment range : ± 15mV
13. Input voltage range : ± 13V
14. Supply voltage rejection ratio : 150 μV/V
15. Output voltage swing: + 13V and – 13V for RL > 2KΩ
16. Output short-circuit current: 25mA
17. supply current: 28mA
18. Power consumption: 85mW
19. Transient response: rise time= 0.3 μs
Overshoot= 5%
LINEAR IC APPLICATIONS LABORATORY 2
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Applications:
1. AC and DC amplifiers
2. Active filters
3. Oscillators
4. Comparators
5. Regulators
IC 555:
Description:
The operation of SE/NE 555 timer directly depends on its internal function.
The three equal resistors R1, R2, R3 serve as internal voltage divider for the source
voltage. Thus one-third of the source voltage VCC appears across each resistor.
Comparator is basically an Op amp which changes state when one of its
inputs exceeds the reference voltage. The reference voltage for the lower
comparator is +1/3 VCC. If a trigger pulse applied at the negative input of this
comparator drops below +1/3 VCC, it causes a change in state. The upper comparator
is referenced at voltage +2/3 VCC. The output of each comparator is fed to the input
terminals of a flip flop.
The flip-flop used in the SE/NE 555 timer IC is a bistable multivibrator. This
flip flop changes states according to the voltage value of its input. Thus if the voltage
at the threshold terminal rises above +2/3 VCC, it causes upper comparator to cause
flip-flop to change its states. On the other hand, if the trigger voltage falls below +1/3
VCC, it causes lower comparator to change its states. Thus the output of the flip flop
is controlled by the voltages of the two comparators. A change in state occurs when
the threshold voltage rises above +2/3 VCC or when the trigger voltage drops below
+1/3 Vcc.
The output of the flip-flop is used to drive the discharge transistor and the
output stage. A high or positive flip-flop output turns on both the discharge transistor
and the output stage. The discharge transistor becomes conductive and behaves as
a low resistance short circuit to ground. The output stage behaves similarly. When
the flip-flop output assumes the low or zero states reverse action takes place i.e., the
discharge transistor behaves as an open circuit or positive VCC state. Thus the
operational state of the discharge transistor and the output stage depends on the
voltage applied to the threshold and the trigger input terminals.
LINEAR IC APPLICATIONS LABORATORY 3
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Block Diagram of IC 555:
Pin Configuration:
Function of Various Pins of 555 IC:
Pin (1) of 555 is the ground terminal; all the voltages are measured with respect to
this pin.
Pin (2) of 555 is the trigger terminal, If the voltage at this terminal is held greater than
one-third of VCC, the output remains low. A negative going pulse from Vcc to less than
Vec/3 triggers the output to go High. The amplitude of the pulse should be able to
make the comparator (inside the IC) change its state. However the width of the
negative going pulse must not be greater than the width of the expected output pulse.
LINEAR IC APPLICATIONS LABORATORY 4
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Pin (3) is the output terminal of IC 555. There are 2 possible output states. In the
low output state, the output resistance appearing at pin (3) is very low (approximately
10 Ω). As a result the output current will goes to zero , if the load is connected from
Pin (3) to ground , sink a current I Sink (depending upon load) if the load is connected
from Pin (3) to ground, and sinks zero current if the load is connected between +VCC
and Pin (3).
Pin (4) is the Reset terminal. When unused it is connected to +Vcc. Whenever the
potential of Pin (4) is drives below 0.4V, the output is immediately forced to low state.
The reset terminal enables the timer over-ride command signals at Pin (2) of the IC.
Pin (5) is the Control Voltage terminal.This can be used to alter the reference levels
at which the time comparators change state. A resistor connected from Pin (5) to
ground can do the job. Normally 0.01μF capacitor is connected from Pin (5) to
ground. This capacitor bypasses supply noise and does not allow it affect the
threshold voltages.
Pin (6) is the threshold terminal. In both astable as well as monostable modes, a
capacitor is connected from Pin (6) to ground. Pin (6) monitors the voltage across
the capacitor when it charges from the supply and forces the already high O/p to Low
when the capacitor reaches +2/3 VCC.
Pin (7) is the discharge terminal. It presents an almost open circuit when the output
is high and allows the capacitor charge from the supply through an external resistor
and presents an almost short circuit when the output is low.
Pin (8) is the +Vcc terminal. 555 can operate at any supply voltage from +3 to
+18V.
Features of 555 IC
1. The load can be connected to o/p in two ways i.e. between pin 3 & ground 1 or
between pin 3 & VCC (supply)
2. 555 can be reset by applying negative pulse, otherwise reset can be connected
to +Vcc to avoid false triggering.
3. An external voltage effects threshold and trigger voltages.
4. Timing from micro seconds through hours.
5. Monostable and bistable operation
6. Adjustable duty cycle
7. Output compatible with CMOS, DTL, TTL
8. High current output sink or source 200mA
LINEAR IC APPLICATIONS LABORATORY 5
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
9. High temperature stability
10. Trigger and reset inputs are logic compatible.
Specifications:
1. Operating temperature : SE 555-- -55oC to 125oC
NE 555-- 0o to 70oC
2. Supply voltage : +5V to +18V
3. Timing : μSec to Hours
4. Sink current : 200mA
5. Temperature stability : 50 PPM/oC change in temp or 0-005% /oC.
Applications:
1. Monostable and Astable Multivibrators
2. dc-ac converters
3. Digital logic probes
4. Waveform generators
5. Analog frequency meters
6. Tachometers
7. Temperature measurement and control
8. Infrared transmitters
9. Regulator & Taxi gas alarms etc.
IC 565:
Description:
The Signetics SE/NE 560 series is monolithic phase locked loops. The SE/NE 560,
561, 562, 564, 565, & 567 differ mainly in operating frequency range, power supply
requirements and frequency and bandwidth adjustment ranges. The device is
available as 14 Pin DIP package and as 10-pin metal can package. Phase
comparator or phase detector compare the frequency of input signal fs with frequency
of VCO output fo and it generates a signal which is function of difference between the
phase of input signal and phase of feedback signal which is basically a d.c voltage
mixed with high frequency noise. LPF remove high frequency noise voltage. Output
is error voltage. If control voltage of VCO is 0, then frequency is center frequency (fo)
and mode is free running mode. Application of control voltage shifts the output
frequency of VCO from fo to f. On application of error voltage, difference between fs
LINEAR IC APPLICATIONS LABORATORY 6
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
& f tends to decrease and VCO is said to be locked. While in locked condition, the
PLL tracks the changes of frequency of input signal.
Block Diagram of IC 565
Pin Configuration:
Specifications:
1. Operating frequency range : 0.001 Hz to 500 KHz
2. Operating voltage range : ±6 to ±12V
3. Inputs level required for tracking : 10mV rms minimum to 3v (p-p)
max.
LINEAR IC APPLICATIONS LABORATORY 7
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
4. Input impedance : 10 KΩ typically
5. Output sink current : 1mA typically
6. Drift in VCO center frequency : 300 PPM/oC typically
(fout) with temperature
7. Drif in VCO centre frequency with : 1.5%/V maximum
supply voltage
8. Triangle wave amplitude : typically 2.4 VPP at ± 6V
9. Square wave amplitude : typically 5.4 VPP at ± 6V
10. Output source current : 10mA typically
11. Bandwidth adjustment range : <±1 to >± 60%
Center frequency fout = 1.2/4R1C1 Hz
= free running frequency
FL = ± 8 fout/V Hz
V = (+V) – (-V)
fc = ±
Applications:
1. Frequency multiplier
2. Frequency shift keying (FSK) demodulator
3. FM detector
IC 566:
Description:
The NE/SE 566 Function Generator is a voltage controlled oscillator of
exceptional linearity with buffered square wave and triangle wave outputs. The
frequency of oscillation is determined by an external resistor and capacitor and the
voltage applied to the control terminal. The oscillator can be programmed over a ten
to one frequency range by proper selection of an external resistance and modulated
over a ten to one range by the control voltage with exceptional linearity.
LINEAR IC APPLICATIONS LABORATORY 8
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Block Diagram of IC566
Pin diagram:
Specifications:
Maximum operating Voltage --- 26V
Input voltage --- 3V (P-P)
Storage Temperature --- -65oC to + 150oC
Operating temperature --- 0oC to +70oC for NE 566
-55oC to +125oC for SE 566
Power dissipation --- 300mv
LINEAR IC APPLICATIONS LABORATORY 9
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Applications:
1. Tone generators.
2. Frequency shift keying
3. FM Modulators
4. clock generators
5. signal generators
6. Function generator
IC 1496
Description:
IC balanced mixers are widely used in receiver IC’s. The IC versions are
usually described as balanced modulators. Typical example of balanced IC
modulator is MC1496. The circuit consists of a standard differential amplifier (formed
by Q5 _ Q6 combination) driving a quad differential amplifier composed of transistor
Q1 – Q4. The modulating signal is applied to the standard differential amplifier
(between terminals 1 and 4). The standard differential amplifier acts as a voltage to
current converter. It produces a current proportional to the modulating signal. Q7 and
Q8 are constant current sources for the differential amplifier Q5 – Q6. The lower
differential amplifier has its emitters connected to the package pins ( 2 & 3) so that an
external emitter resistance may be used. Also external load resistors are employed
at the device output (6 and 12 pins).The output collectors are cross-coupled so that
full wave balanced multiplication takes place. As a result, the output voltage is a
constant times the product of the two input signals.
LINEAR IC APPLICATIONS LABORATORY 10
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Schematic of IC1496:
Pin Configuration:
Applications of MC 1496:
a) Balanced modulator
b) AM Modulator
c) Product Modulator
d) AM Detector
e) Mixer
f) Frequency Doublers.
LINEAR IC APPLICATIONS LABORATORY 11
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
2. OP AMP Applications – Adder, Subtractor,
Comparator Circuits
Aim: To design adder, subtractor and comparator for the given signals by using
operational amplifier.
Apparatus required:
S.No Equipment/Component name Specifications/Value Quantity
1 IC 741 Refer page no 2 1
2 Resistor 1kΩ 4
3 Diode 0A79 2
4 Regulated Power supply (0 – 30V),1A 2
5 Function Generator (.1 – 1MHz), 20V p-p 1
6 Cathode Ray Oscilloscope (0 – 20MHz) 1
7 Multimeter 3 ½ digit display 1
Theory:
Adder: A two input summing amplifier may be constructed using the inverting
mode. The adder can be obtained by using either non-inverting mode or differential
amplifier. Here the inverting mode is used. So the inputs are applied through
resistors to the inverting terminal and non-inverting terminal is grounded. This is
called “virtual ground”, i.e. the voltage at that terminal is zero. The gain of this
summing amplifier is 1, any scale factor can be used for the inputs by selecting
proper external resistors.
Subtractor: A basic differential amplifier can be used as a subtractor as shown in
the circuit diagram. In this circuit, input signals can be scaled to the desired values
by selecting appropriate values for the resistors. When this is done, the circuit is
referred to as scaling amplifier. However in this circuit all external resistors are equal
in value. So the gain of amplifier is equal to one. The output voltage Vo is equal to
the voltage applied to the non-inverting terminal minus the voltage applied to the
inverting terminal; hence the circuit is called a subtractor.
LINEAR IC APPLICATIONS LABORATORY 12
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Comparator: The circuit diagram shows an op-amp used as a comparator. A
fixed reference voltage Vref is applied to the (-) input, and the other time – varying
signal voltage Vin is applied to the (+) input; Because of this arrangement, the circuit
is called the non-inverting comparator. Depending upon the levels of Vin and Vref, the
circuit produces output. In short, the comparator is a type of analog-to-digital
converter. At any given time the output waveform shows whether Vin is greater or
less than Vref. The comparator is sometimes also called a voltage-level detector
because, for a desired value of Vref, the voltage level of the input Vin can be detected
Circuit Diagrams:
Fig 1: Adder
Fig 2: Subtractor
LINEAR IC APPLICATIONS LABORATORY 13
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Fig 3: Comparator
.
Procedures:
A) Adder:
1. Connect the circuit as per the diagram shown in Fig 1.
2. Apply the supply voltages of +15V to pin7 and pin4 of IC741 respectively.
3. Apply the inputs V1 and V2 as shown in Fig 1.
4. Apply two different signals (DC/AC ) to the inputs
5. Vary the input voltages and note down the corresponding output at pin 6 of the IC
741 adder circuit.
6. Notice that the output is equal to the sum of the two inputs.
B) Subtractor:
1. Connect the circuit as per the diagram shown in Fig 2.
2. Apply the supply voltages of +15V to pin7 and pin4 of IC741 respectively.
3 Apply the inputs V1 and V2 as shown in Fig 2.
4. Apply two different signals (DC/AC ) to the inputs
5. Vary the input voltages and note down the corresponding output at pin 6 of the IC
741 subtractor circuit.
6. Notice that the output is equal to the difference of the two inputs.
LINEAR IC APPLICATIONS LABORATORY 14
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
C) Comparator:
1. A fixed reference voltage Vref is applied to the (-) input, and to the other input a
varying voltage Vin is applied as shown in Fig 3.
2. Vary the input voltage above and below the Vref and note down the output at pin 6
of 741 IC.
3. Observe that,
when Vin is less than Vref, the output voltage is -Vsat ( - VEE)
when Vin is greater than Vref, the output voltage is +Vsat (+VCC)
Observations:
Adder:
V1(V) V2(V) Vo(V)
2.5
3.8
2.5
4.0
-5.06
-8.04
Subtractor:
V1(V) V2(V) Vo(V)
2.5
4.1
3.3
5.7
0.8
1.67
Comparator:
Vin(V) Vref(V) Vo(V)
2
5
0.5
7.2
+14
-14
LINEAR IC APPLICATIONS LABORATORY 15
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Model Calculations:
a) Adder
Vo = - (V1 + V2)
If V1 = 2.5V and V2 = 2.5V, then
Vo = - (2.5+2.5) = -5V.
b) Subtractor
Vo = V2 – V1
If V1=2.5 and V2 = 3.3, then
Vo = 3.3 – 2.5 = 0.8V
c) Comparator
If Vin < Vref, Vo = -Vsat - VEE
Vin > Vref, Vo = +Vsat = +VCC
Precautions:
Check the connections before giving the power supply.
Readings should be taken carefully.
Result:
For adder, subtractor and comparator circuits, the practical values are
compared with the theoretical values and they are nearly equal.
Inference:
Different applications of opamp are observed.
Questions & Answers:
1. What is the saturation voltage of 741 in terms of VCC?
Ans: 90% of VCC
2. What is the maximum voltage that can be given at the inputs?
Ans: The inputs must be given in such a way that the output should be less
than Vsat.
LINEAR IC APPLICATIONS LABORATORY 16
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
3. Integrator and Differentiator Circuits using IC 741
Aim: To design and verify the operation of an integrator and differentiator for a
given input.
Apparatus required:
S.No Equipment/Component
name
Specifications/Value Quantity
1 741 IC Refer page no 2 1
2 Capacitors 0.1μf, 0.01μf Each one
3 Resistors 159Ω, 1.5kΩ Each one
4 Regulated Power supply (0 – 30)V,1A 1
5 Function generator (1Hz – 1MHz) 1
6 Cathode Ray Oscilloscope (0 – 20MHz) 1
Theory
Integrator: In an integrator circuit, the output voltage is integral of the input signal.
The output voltage of an integrator is given by Vo = -1/R1Cf
At low frequencies the gain becomes infinite, so the capacitor is fully charged and
behaves like an open circuit. The gain of an integrator at low frequency can be
limited by connecting a resistor in shunt with capacitor.
Differentiator: In the differentiator circuit the output voltage is the differentiation
of the input voltage. The output voltage of a differentiator is given by
Vo = -RfC1 .The input impedance of this circuit decreases with increase in
frequency, thereby making the circuit sensitive to high frequency noise. At high
frequencies circuit may become unstable.
LINEAR IC APPLICATIONS LABORATORY 17
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Circuit Diagrams:
Fig 1: Integrator
Fig 2: Differentiator
LINEAR IC APPLICATIONS LABORATORY 18
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Design equations:
Integrator:
Choose T = 2πRfCf
Where T= Time period of the input signal
Assume Cf and find Rf
Select Rf = 10R1
Vo (p-p) =
Differentiator
Select given frequency fa = 1/(2πRfC1), Assume C1 and find Rf
Select fb = 10 fa = 1/2πR1C1 and find R1
From R1C1 = RfCf, find Cf
Procedures:
Integrator
1. Connect the circuit as per the diagram shown in Fig 1
2. Apply a square wave/sine input of 4V(p-p) at 1KHz
3. Observe the output at pin 6.
4. Draw input and output waveforms as shown in Fig 3.
Differentiator
1. Connect the circuit as per the diagram shown in Fig 2
2. Apply a square wave/sine input of 4V(p-p) at 1KHz
3. Observe the output at pin 6
4. Draw the input and output waveforms as shown in Fig 4
LINEAR IC APPLICATIONS LABORATORY 19
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Wave Forms:
Integrator
Fig 3: Input and output waves forms of integrator
LINEAR IC APPLICATIONS LABORATORY 20
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Differentiator
Fig 4 :Input and output waveforms of Differentiator
LINEAR IC APPLICATIONS LABORATORY 21
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Sample readings:
Integrator
Input –Square wave Output - Triangular
Amplitude(VP-P)
(V)
Time period
(ms)
Amplitude (VP-P)
(V)
Time period
(ms)
8 1 10 1
Input –sine wave Output - cosine
Amplitude(VP-P)
(V)
Time period
(ms)
Amplitude (VP-P)
(V)
Time period
(ms)
8 1 6 1
Differentiator
Input –square wave Output - Spikes
Amplitude (VP-P)
(V)
Time period
(ms)
Amplitude (VP-P)
(V)
Time period
(ms)
8 1 28 1
Input –sine wave Output - cosine
Amplitude (VP-P)
(V)
Time period
(ms)
Amplitude (VP-P)
(V)
Time period
(ms)
8 1 1.8 1
Model Calculations:
Integrator:
For T= 1 msec
fa= 1/T = 1 KHz
fa = 1 KHz = 1/(2πRfCf)
Assuming Cf= 0.1μf, Rf is found from Rf=1/(2πfaCf)
Rf=1.59 KΩ
Rf = 10 R1
R1= 159Ω
LINEAR IC APPLICATIONS LABORATORY 22
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Differentiator
For T = 1 msec
f= 1/T = 1 KHz
fa = 1 KHz = 1/(2πRfC1)
Assuming C1= 0.1μf, Rf is found from Rf=1/(2πfaC1)
Rf=1.59 KΩ
fb = 10 fa = 1/2πR1C1
for C1= 0.1μf;
R1 =159Ω
Precautions: Check the connections before giving the power supply.
Readings should be taken carefully.
Result: For a given square wave and sine wave, output waveforms for integrator
and differentiator are observed.
Inferences: Spikes and triangular waveforms can be obtained from a given
square waveform by using differentiator and integrator respectively.
Questions & Answers:
1. What are the problems of ideal differentiator?
Ans: At high frequencies the differentiator becomes unstable and breaks into
oscillation. The differentiator is sensitive to high frequency noise.
2. What are the problems of ideal integrator?
Ans: The gain of the integrator is infinite at low frequencies.
3. What are the applications of differentiator and integrator?
Ans: The differentiator used in waveshaping circuits to detect high frequency
components in an input signal and also as a rate-of –change detector in FM
demodulators.
The integrator is used in analog computers and analog to digital converters
and signal-wave shaping circuits.
4. What is the need for Rf in the circuit of integrator?
Ans: The gain of an integrator at low frequencies can be limited to avoid the
saturation problem if the feedback capacitor is shunted by a resistance Rf
5. What is the effect of C1 on the output of a differentiator?
Ans: It is used to eliminate the high frequency noise problem.
LINEAR IC APPLICATIONS LABORATORY 23
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
4. Active Filter Applications – LPF, HPF (first order)
Aim: To design and obtain the frequency response of
i) First order Low Pass Filter (LPF)
ii) First order High Pass Filter (HPF)
Apparatus required:
S.No Equipment/Component name Specifications/Value Quantity
1 IC 741 Refer page no 2 1
2 Resistors
Variable Resistor
10k ohm
20kΩ pot
3
1
3 capacitors 0.01μf 1
4 Cathode Ray Oscilloscope (0 – 20MHz) 1
5 Regulated Power supply (0 – 30V),1A 1
6 Function Generator (1Hz – 1MHz) 1
Theory:
a) LPF:
A LPF allows frequencies from 0 to higher cut of frequency, fH. At fH the gain
is 0.707 Amax, and after fH gain decreases at a constant rate with an increase in
frequency. The gain decreases 20dB each time the frequency is increased by 10.
Hence the rate at which the gain rolls off after fH is 20dB/decade or 6 dB/ octave,
where octave signifies a two fold increase in frequency. The frequency f=fH is called
the cut off frequency because the gain of the filter at this frequency is down by 3 dB
from 0 Hz. Other equivalent terms for cut-off frequency are -3dB frequency, break
frequency, or corner frequency.
b) HPF:
The frequency at which the magnitude of the gain is 0.707 times the maximum
value of gain is called low cut off frequency. Obviously, all frequencies higher than fL
are pass band frequencies with the highest frequency determined by the closed –
loop band width all of the op-amp.
LINEAR IC APPLICATIONS LABORATORY 24
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Circuit diagrams:
Fig 1: Low pass filter
Fig 2: High pass filter
Design:
First Order LPF: To design a Low Pass Filter for higher cut off frequency fH = 4 KHz
and pass band gain of 2
fH = 1/( 2πRC )
Assuming C=0.01 µF, the value of R is found from
R= 1/(2πfHC) Ω =3.97KΩ
The pass band gain of LPF is given by AF = 1+ (RF/R1)= 2
Assuming R1=10 KΩ, the value of RF is found from
RF=( AF-1) R1=10KΩ
LINEAR IC APPLICATIONS LABORATORY 25
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
First Order HPF: To design a High Pass Filter for lower cut off frequency
fL = 4 KHz and pass band gain of 2
fL = 1/( 2πRC )
Assuming C=0.01 µF,the value of R is found from
R= 1/(2πfLC) Ω =3.97KΩ
The pass band gain of HPF is given by AF = 1+ (RF/R1)= 2
Assuming R1=10 KΩ, the value of RF is found from
RF=( AF-1) R1=10KΩ
Procedure:
First Order LPF
1. Connections are made as per the circuit diagram shown in Fig 1.
2. Apply sinusoidal wave of constant amplitude as the input such that op-amp does
not go into saturation.
3. Vary the input frequency and note down the output amplitude at each step as
shown in Table (a).
4. Plot the frequency response as shown in Fig 3 .
First Order HPF
1. Connections are made as per the circuit diagrams shown in Fig 2.
2. Apply sinusoidal wave of constant amplitude as the input such that op-amp does
not go into saturation.
3. Vary the input frequency and note down the output amplitude at each step as
shown in Table (b).
4. Plot the frequency response as shown in Fig 4.
LINEAR IC APPLICATIONS LABORATORY 26
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Tabular Form and Sampled Values:
a)LPF b) HPF
Input voltage Vin = 0.5V
Model graphs :
LINEAR IC APPLICATIONS LABORATORY
Frequenc
y
O/P
Voltage(V)
Voltage
Gain
Vo/Vi
Gain
indB
100Hz 0.9 1.8 5.105
200Hz 0.9 1.8 5.105
300Hz 0.9 1.8 5.105
500Hz 0.9 1.8 5.105
750Hz 0.9 1.8 5.105
900Hz 0.9 1.8 5.105
1KHz 0.9 1.8 5.105
2KHz 0.8 1.6 4.08
3KHz 0.75 1.5 3.52
4KHz 0.7 1.4 2.92
5KHz 0.65 1.3 2.27
6KHz 0.55 1.1 0.82
7KHz 0.5 1.0 0
8KHz 0.45 0.9 -0.91
9KHz 0.4 0.8 -1.94
10KHz 0.35 0.7 -3.09
Frequency O/P
Voltage(V)
Voltage
Gain
Vo/Vi
Gain
indB
500Hz 0.12 0.24 -12.39
700Hz 0.16 0.32 -9.89
800Hz 0.2 0.4 -7.95
1KHz 0.24 0.48 -6.38
2KHz 0.4 0.8 -1.938
3KHz 0.55 1.1 0.83
4KHz 0.7 1.4 2.92
5KHz 0.75 1.5 3.52
6KHz 0.8 1.6 4.08
7KHz 0.85 1.7 4.60
8KHz 0.85 1.7 4.60
9KHz 0.85 1.7 4.60
10KHz 0.85 1.7 4.60
27
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Fig (3) Fig(4)
Frequency response characteristics Frequency response characteristics
of LPF of HPF
Precautions:
Check the connections before giving the power supply.
Readings should be taken carefully.
Result: First order low-pass filter and high-pass filter are designed and frequency
response characteristics are obtained.
Inferences: By interchanging R and C in a low-pass filter, a high-pass filter can
be obtained.
Questions & Answers:
1. What is meant by frequency scaling?
Ans: Change of cut off frequency from one value to the other.
2. How do you convert an original frequency (cut off) fH to a new cut off frequency
fH?
Ans: By varying either resistor R or capacitor C values
3. What is the effect of order of the filter on frequency response characteristics?
Ans: Each increase in order will produce -20 dB/decade additional increases in
roll off rate.
4. What modifications in circuit diagrams require to change the order of the filter?
Ans: Order of the filter is changed by RC network.
LINEAR IC APPLICATIONS LABORATORY 28
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
5. Active Filter Applications – BPF & Band Reject
(Wideband ) and Notch Filters
Aim: To design and obtain the frequency response of
i) Wide Band pass filter
ii) Wide Band reject filter
iii) Notch filter
Apparatus required:
S.No Equipment/Component name Specifications/Value Quantity
1 741 IC Refer page no 2 3
2 Resistors
Resistors
5.6kΩ
39kΩ
9
2
3 Resistors (20kΩ pot) 2
4 Capacitors
Capacitors
Capacitors
0.01μf
0.1μf
0.2μf
2
2
15 Regulated Power supply (0 – 30)V,1A 1
6 Function Generator (1Hz – 1MHZ) 1
7 Cathode Ray Oscilloscope (0 – 20MHz) 1
Theory:
Band pass filter : A band pass filter has a pass band between two cutoff
frequencies fH and fL such that fH > fL. Any input frequency outside this pass band is
attenuated. There are two types of band-pass filters. Wide band pass and Narrow
band pass filters. We can define a filter as wide band pass if its quality factor Q <10.
If Q>10, then we call the filter a narrow band pass filter. A wide band pass filter can
be formed by simply cascading high-pass and low-pass sections. The order of band
pass filter depends on the order of high pass and low pass sections.
LINEAR IC APPLICATIONS LABORATORY 29
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Band Rejection Filter : The band-reject filter is also called a band-stop or
band-elimination filter. In this filter, frequencies are attenuated in the stop band while
they are passed outside this band. Band reject filters are classified as wide band-
reject narrow band-reject. Wide band-reject filter is formed using a low pass filter, a
high-pass filter and summing amplifier. To realize a band-reject response, the low
cut off frequency fL of high pass filter must be larger than high cut off frequency fH of
low pass filter. The pass band gain of both the high pass and low pass sections must
be equal.
Notch Filter :
The narrow band reject filter, often called the notch fitter is commonly used for the
rejection of a single frequency. The most commonly used notch filter is the twin-T
network .This is a passive filter composed of two T-shaped networks. One T network
is made up of two resistors and a capacitor, while the other uses two capacitors and
a resistor. There are several ways to make the notch filter. One way is to subtract
the band pass filter output from its input .The notch-out frequency is the frequency at
which maximum attenuation occurs and is given by
fN = 1/( 2πRC )
Circuit diagrams:
Fig 1: Wideband pass filter
LINEAR IC APPLICATIONS LABORATORY 30
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Fig 2: Wideband reject filter
Fig 3: Notch filter
Design:
Band pass filter : To design a band pass filter having fH = 4KHz and fL
= 400Hz and pass band gain of 2.
As shown in Fig 1,the first section consisting of Op Amp,RF,R1,R and C is the high
pass filter and second consisting of low pass filter. The design of low pass and high
pass filters.
Low Pass Filter Design:
LINEAR IC APPLICATIONS LABORATORY 31
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Assuming C’=0.01μf, the value of R’ is found from
R’ = 1/(2πfH C’) Ω =3.97KΩ
The pass band gain of LPF is given by ALPF = 1+ (R’ F / R’1 )=2
Assuming R’1=5.6 KΩ, the value of R’F is found from R’F =( AF-1) R’1=5.6KΩ
High Pass Filter Design:
Assuming C=0.01μf, the value of R is found from
R = 1/(2πfLC) Ω =39.7KΩ
The pass band gain of HPF is given by AHPF = 1+ (RF / R1 )=2
Assuming R1=5.6 KΩ, the value of RF is found from
RF = ( AF-1) R1=5.6KΩ
Band reject filter: To design a band reject filter with fH = 4 KHz, fL = 400Hz
and pass band gain of 2
Low Pass Filter Design:
Assuming C’=0.01μf, the value of R’ is found from
R’ = 1/(2πfH C’) Ω =3.97KΩ
The pass band gain of LPF is given by ALPF = 1+ (R’ F / R’1 )=2
Assuming R’1=5.6 KΩ, the value of R’F is found from
R’F =( AF-1) R’1=5.6KΩ
High Pass Filter Design:
Assuming C=0.01μf, the value of R is found from
R = 1/ (2πfLC) Ω =39.7KΩ
The pass band gain of HPF is given by AHPF = 1+ (RF / R1) =2
Assuming R1=5.6 KΩ, the value of RF is found from
RF = (AF-1) R1=5.6KΩ
Adder circuit design: Select all resistors equal value such that gain is unity.
Assume R2=R3=R4=5.6 KΩ
Notch Filter Design: fN = 400Hz
Assuming C=0.1μf,the value of R is found from
R = 1/ (2πfNC)=39 KΩ
Procedure:
LINEAR IC APPLICATIONS LABORATORY 32
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Wide Band Pass Filter:
1. Connect the circuit as per the circuit diagram shown in Fig1
2. Apply sinusoidal wave of 0.5V amplitude as input such that opamp does not go
into saturation (depending on gain).
3. Vary the input frequency from 100 Hz to 100 KHz and note down the output
amplitude at each step as shown in Table (a).
4. Plot the frequency response as shown in Fig 4.
Wide Band Reject Filter:
1. Connect the circuit as per the circuit diagram shown in Fig 2
2. Apply sinusoidal wave of 0.5V amplitude as input such that opamp
does not go into saturation (depending on gain).
3. Vary the input frequency from 100 Hz to 100 KHz and note down the output
amplitude at each step as shown in Table( b).
4. Plot the frequency response as shown in Fig 5.
Notch Filter:
1. Connect the circuit as per the circuit diagram shown in Fig 3
2. Apply sinusoidal wave of 2Vp-p amplitude as input such that opamp
does not go into saturation (depending on gain).
3. Vary the input frequency from 100 Hz to 4 KHz and note down the output
amplitude at each step as shown in Table( c).
4. Plot the frequency response as shown in Fig 6.
Observations:
LINEAR IC APPLICATIONS LABORATORY 33
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
a) Band pass filter: b) Band Reject Filter
Input voltage (Vi) = 0.5V
c) Notch filter
LINEAR IC APPLICATIONS LABORATORY
Frequeny O/P
Voltage
Vo(V)
Gain
Vo/Vi
Gain
indB
100Hz 0.5 1 0
200Hz 0.9 1.8 5.105
300Hz 1.15 2.3 7.23
400Hz 1.4 2.8 8.94
500Hz 1.5 3 9.54
750Hz 1.6 3.2 10.10
900Hz 1.7 3.4 10.63
1KHz 1.7 3.4 10.63
1.5KHz 1.7 3.4 10.63
2KHz 1.6 3.2 10.10
2.5KHz 1.55 3.1 9.83
3KHz 1.5 3.0 9.54
4KHz 1.4 2.8 8.94
5KHz 1.2 2.4 7.6
6KHz 1.1 2.2 6.84
7KHz 1.0 2.0 6.02
8KHz 0.9 1.8 5.11
9KHz 0.34 1.7 4.60
10KHz 0.28 1.4 2.92
Frequency O/P
Voltage(V)
Gain
Vo/Vi
Gain indB
50Hz 1 2 6.02
70Hz 1 2 6.02
100Hz 1 2 6.02
200Hz 0.9 1.8 5.10
300Hz 0.8 1.6 4.08
400Hz 0.7 1.4 2.92
500Hz 0.6 1.2 1.58
700Hz 0.5 1 0
900Hz 0.28 0.56 -5.03
1KHz 0.22 0.44 -7.13
2KHz 0.28 0.56 -5.056
3KHz 0.44 0.88 -1.11
4KHz 0.56 1.12 0.98
5KHz 0.70 1.4 2.92
6KHz 0.80 1.6 4.08
7KHz 0.85 1.7 4.61
8KHz 0.90 1.8 5.10
9KHz 0.90 1.8 5.10
10KHz 0.90 1.8 5.10
34
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Input voltage=2Vp-p
Model graphs:
Fig 4 : Frequency response of Fig 5 : Frequency response
wide bandpass filter of wide band reject filter
LINEAR IC APPLICATIONS LABORATORY
Frequency O/P
Voltage(V)
Vo/Vi Gain in
dB
100Hz 0.8 0.4 -7.95
200Hz 0.7 0.35 -9.11
300Hz 0.3 0.15 -16.47
400Hz 0.08 0.04 -27.95
500Hz 0.28 0.014 -17.05
600Hz 0.48 0.024 -12.39
700Hz 0.7 0.35 -9.11
800Hz 0.8 0.4 -7.95
900Hz 0.8 0.4 -7.95
1 KHz 0.8 0.4 -7.95
2 KHz 0.8 0.4 -7.95
3 KHz 0.8 0.4 -7.95
4 KHz 0.8 0.4 -7.95
35
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Fig 6: Frequency response of notch filter
Precautions:
Check the connections before giving the power supply.
Readings should be taken carefully.
Result:
i) The frequency response of wide band pass filter is plotted as shown in Fig 4.
ii) The frequency response of wide band reject filter is plotted as shown in Fig 5.
iii) The frequency response of notch filter is plotted as shown in Fig 6
Inferences: Cascade connection of HPF and LPF produces wideband pass filter
and parallel connection of the above filters gives wideband reject filter. The notch
filter is used to reject the single frequency.
Questions & Answers:
1. What is the relation between fC & fH, fL?
Ans:
2. How do you increase the gain of the wideband pass filter?
Ans: By increasing the gain of either LPF or HPF
3. What is the application of Notch filter?
Ans: The rejection of single frequency such as the 50-Hz power line frequency
hum
LINEAR IC APPLICATIONS LABORATORY 36
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
4. What is the order of the filter (each type) ?.What modifications you suggest for the
Ans: circuit diagram to increase the order of the filter?
Order of the BPF & BRF’S are the order of the HPF & LPF..Order of the
BPF& BRF’s are increased by increasing order of HPF&LPF.
5. What is the gain roll off outside the pass band?
Ans: Gain roll off outside the pass band is (20n) db/dec where ’n’ indicates the
order of the filter.
6. What is the difference between active and passive filters?
Ans: Active filters use Op Amp as active element, and resistors and capacitors as
the passive elements.
7. What are the advantages of active filters over passive filters?
Ans: Gain and frequency adjustment.
No loading problem.
Low cost
LINEAR IC APPLICATIONS LABORATORY 37
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
6. IC 741 Oscillator Circuits
Phase Shift and Wien Bridge Oscillators
Aim: To design (i) phase shift and (ii) Wien Bridge oscillators for the given
frequency of oscillation and verify it practically.
Apparatus required:
S.No Equipment/Component
name
Specifications/Value Quantity
1 IC 741 Refer page no 2 1
2 Resistors
Variable Resistor
1.3 KΩ,3.18 KΩ
13KΩ, ,31.8 KΩ
500 KΩ pot
Each Three
Each one
13 Capacitors 0.1 µF
0.01 µF
3
2
4 Regulated Power supply (0 – 30V),1A 1
5 Cathode Ray Oscilloscope (0 -20MHz) 1
Theory:
The μA741 is a high performance monolithic operational amplifier constructed
using the planar epitaxial process. High common mode voltage range and absence
of latch-up tendencies make the μA741 ideal for use as voltage follower. The high
gain and wide range of operating voltage provides superior performance in integrator,
summing amplifier and general feedback applications.
In the phase shift oscillator, out of 360o phase shift, 180o phase shift is
provided by the op-amp and another 180o is by 3 RC networks. In the Weinbridge
oscillator, the balancing condition of the bridge provides the total 360o phase shift.
LINEAR IC APPLICATIONS LABORATORY 38
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Circuit Diagrams:
Fig 1 : RC Phase shift oscillator
Fig 2: Wien Bridge oscillator
LINEAR IC APPLICATIONS LABORATORY 39
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Design:
1. Phase shift oscillator
To design a phase shift oscillator with fo =500 Hz
fo = 1/(2πRC )
and gain= RF/R1= 29
Assuming C = 0.1 µF,the value of R is found from
R = 1/ (2π foC ) = 1.3 KΩ
Take R1 = 10R =13 KΩ
RF = 29R1 (use 500K pot)
2. Wien bridge Oscillator
To design a Wien bridge oscillator with fo =5 KHz
fo = 1/2πRC and RF = 2R1
Assuming C = 0.01 µF,the value of R is found from
R= 1/2πfc= 3.18 KΩ
Take R1 = 10 R=31.8 KΩ
RF = 2R1 (use 100K pot)
Procedure:
1. Phase shift oscillator
1. Connect the circuit as per the circuit diagram shown in Fig 1
2. Observe the output waveform on the CRO.
3. Vary the potentiometer to get the undistorted waveform as shown Fig a.
4. Measure the time period and amplitude of the output waveform.
5. Plot the waveforms on a graph sheet.
2. Wien bridge Oscillator
1. Connect the circuit as per the circuit diagram shown in Fig 2
2. Observe the output waveform on the CRO.
3. Vary the potentiometer to get the undistorted waveform as shown in Fig b
4. Measure the time period and amplitude of the output waveform.
5. Plot the waveforms on a graph sheet
LINEAR IC APPLICATIONS LABORATORY 40
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Waveforms:
Fig (a): RC Phase Shift Oscillator
Fig (b): Wien Bridge Oscillator
Tabular form:
1. Phase shift oscillator:
S.No Amplitude(VP-P) Time period
(ms)
Practical frequency
(Hz)
Theoretical
frequency (Hz)
1 20V 2.2 454 500
2. Wien bridge Oscillator:
S.No Amplitude(VP-P) Time period
(ms)
Practical frequency
(Hz)
Theoretical frequency
(Hz)
1 20V 0.22ms 4.545KHz 5KHz
LINEAR IC APPLICATIONS LABORATORY 41
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Precautions:
Check the connections before giving the power supply.
Readings should be taken carefully.
Result:
RC phase shift and Wien bridge oscillators are designed and output
waveforms are observed as shown in Fig (a) and (b).
Inferences:
Sinusoidal waveforms can be deigned by using RC phase shift and Wien-
Bridge oscillators.
Questions & Answers:
1 What is an oscillator?
Ans: Oscillator is a circuit that generates a repetitive waveform of fixed
amplitude and frequency without any external input signal.
2 How do you change the frequency of oscillation in RC phase shift and
Ans: Wien bridge oscillators?
By varying either resistor R or capacitor C values
3 What are the applications of oscillators?
Ans: Oscillators are used in radio, television, computers, and communications
4 What is the advantage of using opamp in the oscillator circuit?
Ans: Opamp is used to generate a variety of output wave forms.
5 How do you achieve fine variations in fo ?
Ans: Fine variations in fo can be achieved by changing C value.
6 How do you achieve coarse variations in fo ?
Ans: Coarse variations in fo can be achieved by changing R value
LINEAR IC APPLICATIONS LABORATORY 42
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
7. Function Generator using OPAMPs
Aim: To generate square wave and triangular wave form by using OPAMPs.
Apparatus required:
S.No Equipment/Component name Specifications/Value Quantity
1 741 IC Refer page no 2 2
2 Capacitors 0.01μf,0.001μf Each one
3 Resistors
Resistors
86kΩ ,68kΩ ,680kΩ
100kΩ
Each one
2
4 Regulated Power supply (0 – 30V),1A 1
5 Cathode Ray Oscilloscope (0 -20MHz) 1
Theory: Function generator generates waveforms such as sine, triangular, square
waves and so on of different frequencies and amplitudes. The circuit shown in Fig1
is a simple circuit which generates square waves and triangular waves
simultaneously. Here the first section is a square wave generator and second
section is an integrator. When square wave is given as input to integrator it produces
triangular wave.
Circuit Diagram:
Fig1: Function generator
LINEAR IC APPLICATIONS LABORATORY 43
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Design:
Square wave Generator:
T= 2RfC ln (2R2 +R1/ R1)
Assume R1 = 1.16 R2
Then T= 2RfC
Assume C and find Rf
Assume R1 and find R2
Integrator:
Take R3 Cf >> T
R3 Cf = 10T
Assume Cf find R3
Take R3Cf = 10T
Assume Cf = 0.01μf
R3 = 10T/C
= 20KΩ
Procedure:
1. Connect the circuit as per the circuit diagram shown above.
2. Obtain square wave at A and Triangular wave at Vo2 as shown in Fig 1.
3. Draw the output waveforms as shown in Fig 2(a) and (b).
Model Calculations:
For T= 2 m sec
T = 2 Rf C
Assuming C= 0.1μf
Rf = 2.10-3/ 2.01.10-6
= 10 KΩ
Assuming R1 = 100 K
R2 = 86 KΩ
Sample readings:
Square Wave:
Vp-p = 26 V(p-p)
T = 1.8 msec
Triangular Wave:
Vp-p = 1.3 V
T= 1.8 msec
LINEAR IC APPLICATIONS LABORATORY 44
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Wave Forms:
Fig 2 (a): Output at ‘A’
(b): Output at V02
Precautions:
Check the connections before giving the power supply.
Readings should be taken carefully.
.
Result: Square wave and triangular wave are generated and the output
waveforms are observed.
Inferences: Various waveforms can be generated.
Questions & Answers:
1. How do you change the frequency of square wave?
Ans: By changing resistor and capacitor values
2. What are the applications of function generator?
Ans: Function generators are used for Transducer linearization and sine
shaping.
LINEAR IC APPLICATIONS LABORATORY 45
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
8. IC 555 Timer-Monostable Operation Circuit
Aim: To generate a pulse using Monostable Multivibrator by using IC555
Apparatus required:
S.No Equipment/Component
name
Specifications/Value Quantity
1 555 IC Refer page no 6 1
2 Capacitors 0.1μf,0.01μf Each one
3 Resistor 10kΩ 1
4 Regulated Power supply (0 – 30V),1A 1
5 Function Generator (1HZ – 1MHz) 1
6 Cathode ray oscilloscope (0 – 20MHz) 1
Theory: A Monostable Multivibrator, often called a one-shot Multivibrator, is a
pulse-generating circuit in which the duration of the pulse is determined by the RC
network connected externally to the 555 timer. In a stable or stand by mode the
output of the circuit is approximately Zero or at logic-low level. When an external
trigger pulse is obtained, the output is forced to go high ( VCC). The time for which
the output remains high is determined by the external RC network connected to the
timer. At the end of the timing interval, the output automatically reverts back to its
logic-low stable state. The output stays low until the trigger pulse is again applied.
Then the cycle repeats. The Monostable circuit has only one stable state (output
low), hence the name monostable. Normally the output of the Monostable
Multivibrator is low.
LINEAR IC APPLICATIONS LABORATORY 46
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Circuit Diagram:
Fig1: Monostable Circuit using IC555
Design:
Consider VCC = 5V, for given tp
Output pulse width tp = 1.1 RA C
Assume C in the order of microfarads & Find RA
Typical values:
If C=0.1 µF , RA = 10k then tp = 1.1 mSec
Trigger Voltage =4 V
Procedure:
1. Connect the circuit as shown in the circuit diagram.
2. Apply Negative triggering pulses at pin 2 of frequency 1 KHz.
3. Observe the output waveform and measure the pulse duration.
4. Theoretically calculate the pulse duration as Thigh=1.1. RAC
5. Compare it with experimental values.
LINEAR IC APPLICATIONS LABORATORY 47
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Waveforms:
Fig 2 (a): Trigger signal
(b): Output Voltage
(c): Capacitor Voltage
Sample Readings:
Precautions:
Check the connections before giving the power supply.
Readings should be taken carefully.
Result: The input and output waveforms of 555 timer monostable Multivibrator are
observed as shown in Fig 2(a), (b), (c).
LINEAR IC APPLICATIONS LABORATORY
Trigger Output wave Capacitor output
0 to 5V range
1)1V,0.09msec
0 to 5V range
4.6V, 0.5msec
0 to 3.33 V range
3V, 0.88 msec
48
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Inferences: Output pulse width depends only on external components RA and C
connected to IC555.
Questions & Answers:
1. Is the triggering given is edge type or level type? If it is edge type, trailing or
raising edge?
Ans: Edge type and it is trailing edge
2. What is the effect of amplitude and frequency of trigger on the output?
Ans: Output varies proportionally.
3. How to achieve variation of output pulse width over fine and course ranges?
Ans: One can achieve variation of output pulse width over fine and course ranges
by varying capacitor and resistor values respectively
4. What is the effect of Vcc on output?
Ans: The amplitude of the output signal is directly proportional to Vcc
5. What are the ideal charging and discharging time constants (in terms of R and C)
of capacitor voltage?
Ans: Charging time constant T=1.1RC Sec
Discharging time constant=0 Sec
6. What is the other name of monostable Multivibrator? Why?
Ans: i) Gating circuit .It generates rectangular waveform at a definite time and
thus could be used in gate parts of the system.
ii) One shot circuit. The circuit will remain in the stable state until a trigger pulse is
received. The circuit then changes states for a specified period, but then it returns
to the original state.
7. What are the applications of monostable Multivibrator?
Ans: Missing Pulse Detector, Frequency Divider, PWM, Linear Ramp Generator
LINEAR IC APPLICATIONS LABORATORY 49
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
9. IC 555 Timer - Astable Operation Circuit
Aim: To generate unsymmetrical square and symmetrical square waveforms using
IC555.
Apparatus required:
S.No Equipment/Component name Specifications/Value Quantity
1 IC 555 Refer page no 6 1
2 Resistors 3.6kΩ,7.2kΩ Each one
3 Capacitors 0.1μf,0.01μf Each one
4 Diode OA79 1
5 Regulated Power supply (0 – 30V),1A 1
6 Cathode Ray Oscilloscope (0 – 20MHz) 1
Theory:
When the power supply VCC is connected, the external timing capacitor ‘C”
charges towards VCC with a time constant (RA+RB) C. During this time, pin 3 is high
(≈VCC) as Reset R=0, Set S=1 and this combination makes =0 which has
unclamped the timing capacitor ‘C’.
When the capacitor voltage equals 2/3 VCC, the upper comparator triggers the
control flip flop on that =1. It makes Q1 ON and capacitor ‘C’ starts discharging
towards ground through RB and transistor Q1 with a time constant RBC. Current also
flows into Q1 through RA. Resistors RA and RB must be large enough to limit this
current and prevent damage to the discharge transistor Q1. The minimum value of
RA is approximately equal to VCC/0.2 where 0.2A is the maximum current through the
ON transistor Q1.
During the discharge of the timing capacitor C, as it reaches VCC/3, the lower
comparator is triggered and at this stage S=1, R=0 which turns =0. Now =0
unclamps the external timing capacitor C. The capacitor C is thus periodically
charged and discharged between 2/3 VCC and 1/3 VCC respectively. The length of
time that the output remains HIGH is the time for the capacitor to charge from 1/3 VCC
to 2/3 VCC.
The capacitor voltage for a low pass RC circuit subjected to a step input of VCC
volts is given by VC = VCC [1- exp (-t/RC)]
LINEAR IC APPLICATIONS LABORATORY 50
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Total time period T = 0.69 (RA + 2 RB) C
f= 1/T = 1.44/ (RA + 2RB) C
Circuit Diagram:
Fig.1 555 Astable Circuit
Design:
Formulae: f= 1/T = 1.44/ (RA+2RB) C
Duty cycle (D) = tc/T = RA + RB/(RA+2RB)
LINEAR IC APPLICATIONS LABORATORY 51
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Procedure:
I) Unsymmetrical Square wave
1. Connect the circuit as per the circuit diagram shown without connecting the
diode OA 79.
2. Observe and note down the waveform at pin 6 and across timing capacitor.
3. Measure the frequency of oscillations and duty cycle and then compare with
the given values.
4. Sketch both the waveforms to the same time scale.
II) Symmetrical square waveform generator:
1. Connect the diode OA79 as shown in Figure to get D=0.5 or 50%.
2. Choose Ra=Rb = 10KΩ and C=0.1μF
3. Observe the output waveform, measure frequency of oscillations and the duty
cycle and then sketch the o/p waveform.
Model calculations:
Given f=1 KHz. Assuming c=0.1μF and D=0.25
1 KHz = 1.44/ (RA+2RB) x 0.1x10-6 and 0.25 =( RA+RB)/ (RA+2RB)
Solving both the above equations, we obtain RA & RB as
RA = 7.2K Ω
RB = 3.6K Ω
LINEAR IC APPLICATIONS LABORATORY 52
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Waveforms:
Fig 2(a): Unsymmetrical square wave output
(b): Capacitor voltage of Unsymmetrical square wave output
(c): Symmetrical square wave output
Sample Readings:
Parameter Unsymmetrical Symmetrical
Voltage VPP 5V 5V
Time period T
Tc=0.8ms
td=0.2ms
1 ms
Tc = 0.5ms
td = 0.5ms
1 ms
Duty cycle 80% 50%
Precautions:
Check the connections before giving the power supply.
Readings should be taken carefully.
LINEAR IC APPLICATIONS LABORATORY 53
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Result: Both unsymmetrical and symmetrical square waveforms are obtained and
time period at the output is calculated.
Inferences: Unsymmetrical square wave of required duty cycle and symmetrical
square waveform can be generated.
Questions & Answers:
1. What is the effect of C on the output?
Ans: Time period of the output depends on C
2. How do you vary the duty cycle?
Ans: By varying R A or RB.
3. What are the applications of 555 in astable mode?
Ans: FSK Generator, Pulse Position Modulator, Square wave generator
4. What is the function of diode in the circuit?
Ans: To get symmetrical square wave.
5. On what parameters Tc and Td designed?
Ans: R A , RB and C
6. What are charging and discharging times
Ans: The time during which the capacitor charges from (1/3) Vcc to (2/3) Vcc
is equal to the time the output is high is known as charging time and is
given by Tc=0.69(RA+RB)C
The time during which the capacitor discharges from (2/3) Vcc to (1/3) Vcc is
equal to the time the output is low is known as discharging time and is given
by Td=0.69(RB) C.
10. Schmitt Trigger Circuits- using IC 741 & IC 555
LINEAR IC APPLICATIONS LABORATORY 54
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Aim: To design the Schmitt trigger circuit using IC 741 and IC 555
Apparatus required:
S.No Equipment/Component
name
Specifications/Value Quantity
1 IC 741 Refer page no 2 1
2 555IC Refer page no 6 1
3 Cathode Ray Oscilloscope (0 – 20MHz) 1
4 Multimeter 1
5 Resistors 100 Ω
56 KΩ
2
1
6 Capacitors 0.1 μf, 0.01 μf Each one
7 Regulated power supply (0 -30V),1A 1
Theory:
The circuit shows an inverting comparator with positive feed back. This circuit
converts orbitrary wave forms to a square wave or pulse. The circuit is known as the
Schmitt trigger (or) squaring circuit. The input voltage V in changes the state of the
output Vo every time it exceeds certain voltage levels called the upper threshold
voltage Vut and lower threshold voltage Vlt.
When Vo= - Vsat, the voltage across R1 is referred to as lower threshold
voltage, Vlt. When Vo=+Vsat, the voltage across R1 is referred to as upper threshold
voltage Vut.
The comparator with positive feed back is said to exhibit hysterisis, a dead
band condition.
Circuit Diagrams:
LINEAR IC APPLICATIONS LABORATORY 55
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Fig 1: Schmitt trigger circuit using IC 741
Fig 2: Schmitt trigger circuit using IC 555
Design:
Vutp = [R1/(R1+R2 )](+Vsat)
Vltp = [R1/(R1+R2 )](-Vsat)
Vhy = Vutp – Vltp
=[R1/(R1+R2)] [+Vsat – (-Vsat)]
Procedure:
1. Connect the circuit as shown in Fig 1 and Fig2.
LINEAR IC APPLICATIONS LABORATORY 56
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
2. Apply an orbitrary waveform (sine/triangular) of peak voltage greater than UTP to
the input of a Schmitt trigger.
3. Observe the output at pin6 of the IC 741 and at pin3 of IC 555 Schmitt trigger
circuit by varying the input and note down the readings as shown in Table 1 and
Table 2
4. Find the upper and lower threshold voltages (Vutp, VLtp) from the output wave form.
Wave forms:
Fig 3: (a) Schmitt trigger input wave form
(b) Schmitt trigger output wave form
Sample readings:
Table 1:
Parameter Input Output
741 555 741 555
Voltage( Vp-p) 3.6 4 24.8 4.4
Time period(ms) 0.72 1 0.72 1
Table 2:
Parameter 741 555
Vutp 0.2V 0.4V
LINEAR IC APPLICATIONS LABORATORY 57
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Vltp -0.05 -0.4V
Precautions:
Check the connections before giving the power supply.
Readings should be taken carefully.
Results:
UTP and LTP of the Schmitt trigger are obtained by using IC 741 and IC 555 as
shown in Table 2.
Inferences: Schmitt trigger produces square waveform from a given signal.
Questions & Answers:
1. What is the other name for Schmitt trigger circuit?
Ans: Regenerative comparator
2. In Schmitt trigger which type of feed back is used?
Ans: Positive feedback.
3. What is meant by hysteresis?
Ans: The comparator with positive feedback is said to be exhibit hysteresis, a
deadband condition. When the input of the comparator is exceeds Vutp, its
output switches from + Vsat to - Vsat and reverts back to its original state,+
Vsat ,when the input goes below Vltp
4. What are effects of input signal amplitude and frequency on output?
Ans: The input voltage triggers the output every time it exceeds certain voltage
levels (UTP and LTP). Output signal frequency is same as input signal frequency.
11. IC 565- PLL Applications
LINEAR IC APPLICATIONS LABORATORY 58
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Aim: To design a frequency multiplier using IC 565
Apparatus required:
S.No Equipment/Component
name
Specifications/Value Quantity
1 IC 565 Refer page no 8 1
2 IC 555 Refer page no 6 1
3 Resistors 12KΩ,54.5 KΩ Each one
4 Capacitors 0.01μF
0.1 μF
10μF
2
1
15 Regulated power supply (0 -30V),1A 1
6 Cathode Ray Oscilloscope (0 – 20MHz) 1
Theory:
The frequency divider is inserted between the VCO and the phase
comparator of PLL. Since the output of the divider is locked to the input frequency f IN,
the VCO is actually running at a multiple of the input frequency .The desired amount
of multiplication can be obtained by selecting a proper divide– by – N network ,where
N is an integer. To obtain the output frequency fOUT=2fIN, N = 2 is chosen. One must
determine the input frequency range and then adjust the free running frequency fOUT
of the VCO by means of R1 and C1 so that the output frequency of the divider is
midway within the predetermined input frequency range. The output of the VCO now
should be 2fIN . The output of the VCO should be adjusted by varying potentiometer
R1. A small capacitor is connected between pin7 and pin8 to eliminate possible
oscillations. Also, capacitor C2 should be large enough to stabilize the VCO
frequency.
Circuit diagram
LINEAR IC APPLICATIONS LABORATORY 59
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Fig.1 PLL as Frequency Multiplier
Design:
If C= 0.01μF and the frequency of input trigger signal is 2KHz, output pulse
width of 555 in monostable mode is given by
1.1RAC = 1.2T =1.2/f
RA= 1.2/(1.1Cf)=54.5KΩ
fIN=fOUT/N
Under locked conditions,
fOUT = NfIN = 2fIN = 4KHz
Procedure:
1. The circuit is connected as per the circuit diagram.
LINEAR IC APPLICATIONS LABORATORY 60
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
2. Apply a square wave input to the pin2 of the 565
3. Observe the output at pin4 of 565 under locked condition.
4. Give the output of 565 to the pin2 of 555 IC.
5. Observe the output of 555 at pin3.
6. Now give the output of 555 as feedback to the pin5 of the 565.
7. Observe the frequency of output signal fo at pin4 of 565 IC.
8. Draw the wave forms.
Wave forms:
Fig 2(a): Input
(b): PLL output under locked conditions without 555
(c): Output at pin4 of 565 with 555 connected in the feedback
Sample readings:
Parameter Input Output
Amplitude (Vp-p) 8 8
Frequency (KHz) 2 4
LINEAR IC APPLICATIONS LABORATORY 61
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
Precautions:
Check the connections before giving the power supply.
Readings should be taken carefully.
.
Result:
Frequency multiplier using IC 565 is obtained.
Inferences:
Application of IC 555 in monostable mode as a frequency divider is observed
while designing the frequency multiplier.
Questions & Answers:
1. Out of capture and lock ranges, which is smaller?
Ans: Capture range
2. What is the function of VCO in a PLL?
Ans: To get stable oscillations
3. What does happen if frequency divider network -by- 4 is placed in the
feedback?
Ans: Frequency multiplier of 4 is obtained at the output.
12. IC 566 – VCO Applications
Aim: i) To observe the applications of VCO-IC 566
LINEAR IC APPLICATIONS LABORATORY 62
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA
ii) To generate the frequency modulated wave by using IC 566
Apparatus required:
S.No Equipment/Component Name Specifications/Value Quantity
1 IC 566 Refer page no 10 1
2 Resistors 10KΩ
1.5KΩ
2
1
3 Capacitors 0.1 μF
100 pF
1
1
4 Regulated power supply 0-30 V, 1 A 1
5 Cathode Ray Oscilloscope 0-20 MHz 1
6 Function Generator 0.1-1 MHz 1
Theory: The VCO is a free running Multivibrator and operates at a set frequency fo
called free running frequency. This frequency is determined by an external timing
capacitor and an external resistor. It can also be shifted to either side by applying a
d.c control voltage vc to an appropriate terminal of the IC. The frequency deviation is
directly proportional to the dc control voltage and hence it is called a “voltage
controlled oscillator” or, in short, VCO.
The output frequency of the VCO can be changed either by R1, C1 or the
voltage VC at the modulating input terminal (pin 5). The voltage VC can be varied by
connecting a R1R2 circuit. The components R1 and C1 are first selected so that VCO
output frequency lies in the centre of the operating frequency range. Now the
modulating input voltage is usually varied from 0.75 VCC which can produce a
frequency variation of about 10 to 1.
Circuit Diagram:
LINEAR IC APPLICATIONS LABORATORY 63
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING DRS & SKA