Electronics Circuit Lab Manual

Course Code : BECCEC 306R02

Course Name : Electronic Circuits laboratory

List of Experiments:

1. Q point calculation of emitter feedback, collector feedback and voltage divider

bias using BJT.

2. Frequency response characteristics of RC coupled amplifier using BJT.

3. Frequency response characteristics of direct coupled amplifier using BJT.

4. Frequency response of Common Collector amplifier

5. Transistor, FET and MOSFET as a switch.

6. Differential amplifier using FET and BJT

7. Frequency response of current series amplifier ( with and without feedback)

8. Frequency response characteristics of single tuned amplifier

9. Frequency response characteristics of complementary symmetry push-pull

amplifier.

10. Audio frequency oscillator for a specified frequency of oscillation.

11. Relaxation oscillator using UJT

12. Frequency response characteristics of Cascode amplifier

EX NO:1 DATE:

Q POINT CALCULATION AIM:

To find Q point of Emitter feedback, Collector feedback and Voltage divider bias using

BJT for a given IC = --------------- and VCE = -----------------

CIRCUIT DIAGRAM:

Emitter feedback bias

Collector feedback bias

Voltage divider bias

PROCEDURE:

1. For the given IC and VCE calculate the values of the various resistors.

2. Connect the circuit in the bread board and verify the practical values of IC and VCE with

the given values.

RESULT:

R1

R2 R

E

RC

+VCC

Input

Output

I1

I2 I

E

IB

IC

EX NO: 2 DATE:

RC COUPLED AMPLIFIER AIM:

(i)To construct and draw the frequency response characteristics of RC coupled

Amplifier using BJT

(ii) To calculate the band width and quality factor

CIRCUIT DIAGRAM:

DESIGN:

Design of RC coupled amplifier.

The design of a single stage RC coupled amplifier is shown below.

The nominal value of collector current Ic and hfe (β)can be obtained from the datasheet

of the transistor.

Design of Re and Rc.

Let voltage across Re; VRe = 10%Vcc ………….(1)

Voltage across Rc; VRc = 40% Vcc. ……………..(2)

The remaining 50% will drop across the collector-emitter.

From (1) and (2) Rc =0.4 (Vcc/Ic) and Re = 0.1(Vcc/Ic).

Design of R1 and R2.

Base current Ib = Ic/hfe.

Let Ic ≈ Ie .

Let current through R1; IR1 = 10Ib.

Also voltage across R2 ; VR2 must be equal to Vbe + VRe. From this VR2 can be found.

There fore VR1 = Vcc-VR2. Since VR1 ,VR2 and IR1 are found.

we can find R1 and R2 using the following equations.

R1 = VR1/IR1 and R2 = VR2/IR1.

Finding Ce.

Impedance of emitter by-pass capacitor should be one by tenth of Re.

i.e, XCe = 1/10 (Re).

Also XCe = 1/2πFCe.

F can be selected to be 100Hz.

From this Ce can be found.

Finding Cin.

Impedance of the input capacitor (Cin) should be one by tenth of the transistors input

impedance (Rin).

i.e, XCin = 1/10 (Rin)

Rin = R1 parallel R2 parallel (1 + (hfe re))

re = 25mV/Ie.

XCin = 1/2πFCin.

From this Cin can be found.

Finding Cout.

Impedance of the output capacitor (Cout) must be one by tenth of the circuit’s output

resistance (Rout).

i.e, XCout = 1/10 (Rout).

Rout = Rc.

XCout = 1/ 2πFCout.

From this Cout can be found.

Setting the gain.

Introducing a suitable load resistor RL across the transistor’s collector and ground will

set the gain.

Expression for the voltage gain (Av) of a common emitter transistor amplifier is as

follows.

Av = -(rc/re)

re = 25mV/Ie

and rc = Rc parallel RL

MODEL GRAPH

PROCEDURE:

1. Construct the circuit as shown in the Fig.

2. Set the input sine wave value in the millvolts range using AFO

3. Vary the frequency from the AFO and note the output Vo in the CRO.

4. By taking the frequency in X-axis and gain in Y-axis draw the graph.

5. Note the lower and upper cutoff frequency by drawing the 3db line

6. From these two frequencies calculate the band width of the single stage RC coupled

amplifier.

TABULATION:

Vin =

RESULT:

S.No Frequency

in Hz

Amplitude of

the output

voltage

(Vo)

Gain

(A=Vo/Vin)

Gain in db

20log(A)

EX NO: 3 DATE:

DIRECT COUPLED AMPLIFIER AIM:

To construct and draw the frequency response characteristics of Direct coupled

amplifier using BJT

CIRCUIT DIAGRAM:

MODEL GRAPH:

PROCEDURE:

1. Construct the circuit as shown in the Fig.

2. Set the input value in the millvolts range using AFO

3. Vary the frequency from the AFO and note the output Vo in the CRO.

4. By taking the frequency in X-axis and gain in Y-axis draw the graph.

5. Note the lower and upper cutoff frequency by drawing the 3db line

6. From these two frequencies calculate the band width of the single stage RC coupled

amplifier

TABULATION:

Vin =

RESULT:

S.No Frequency

in Hz

Amplitude of

the output

voltage

(Vo)

Gain

(A=Vo/Vin)

Gain in db

20log(A)

EX NO: 4 DATE:

COMMON COLLECTOR AMPLIFIER AIM:

To construct and draw the frequency response characteristics of Common

collector amplifier using BJT

CIRCUIT DIAGRAM:

MODEL GRAPH

PROCEDURE:

1. Give the connections as per the circuit diagram.

2. Set the magnitude of the input waveform to 0.4 V (Peak to Peak).

3. Vary the frequency from the signal generator and note the corresponding

magnitude of the output voltage from the CRO.

4. Calculate the gain using the formula A = Vo/Vin

5. Plot the frequency response (Gain Vs Frequency) in the semi log sheet.

TABULATION:

Vin =

S.No

.

Frequency

(HZ)

Ouput Voltage

VO (Volts)

Gain

20 log(A=Vo/Vin) dB

RESULT:

EX NO: 5 DATE:

TRANSISTOR, FET AND MOSFET AS A SWITCH

AIM:

To construct and verify the working of transistor, FET and MOSFET as a switch.

CIRCUIT DIAGRAM:

Transistor as a switch

FET as a switch

MOSFET as a switch

PROCEDURE:

1. Give the connections as shown in the figure.

2. Give a square wave input of 1V and see the output at, the collector terminal for

BJT, drain terminal for FET and MOSFET.

3. Draw the input and output waveforms in the graph.

TABULATION:

No.of divisions

in the X axis

Time/div Total time

period(ms)

No.of divisions

in the Y axis

Volt/div Total

voltage(V)

Input

Output

RESULT:

EX NO: 6 DATE:

DIFFERENTIAL AMPLIFIER USING BJT AND FET

AIM:

To construct and find the figure of merit of differential amplifier using BJT and

FET.

CIRCUIT DIAGRAM:

Basic differential amplifier using BJT

Differential mode

Common mode

Basic differential amplifier using FET

Differential mode

Common mode

PROCEDURE:

1. Give the connections as shown in the figure.

2. For the differential mode give two different inputs V1 and V2 at the base of Q1 and Q2

respectively and see the output Vo between the two collector terminals.

3. Calculate the differential mode gain using the formula Ad = Vo / (V2-V1)

4. For the common mode give same input Vin at the base of Q1 and Q2

respectively and see the output Vo between the two collector terminals.

5. Calculate the common mode gain using the formula Ac = Vo / (Vin)

6. Calculate the common mode rejection ratio (CMRR) using the formula | Ad /Ac|

TABULATION:

Differential mode

S.No Input V1(mV) Input V2(mV) Output Vo(V) Ad = Vo / (V2-V1)

Common mode

S.No Input Vin (V) Output Vo(V) Ac = Vo / (Vin)

RESULT:

EX NO: 7 DATE:

CURRENT SERIES AMPLIFIER

AIM:

(i)To construct and draw the frequency response of current series amplifier using

BJT.

(ii) To find the bandwidth with and without feedback

CIRCUIT DIAGRAM:

MODEL GRAPH:

PROCEDURE:

1. Construct the circuit as shown in the Fig.

2. Set the input value in the millvolts range using AFO

3. Vary the frequency using the AFO and note the output Vo in the CRO.

4. By taking the frequency in X-axis and gain in Y-axis draw the graph.

5. Note the lower and upper cutoff frequency by drawing the 3db line

6. From these two frequencies calculate the band width of the direct coupled

amplifier.This gives the bandwidth without feedback.

7. Remove the by pass capacitor CE and repeat the procedure from step 2 till step 5.

8. Calculate the band width .This gives the bandwidth with feedback.

TABULATION:

Vin =

S.No Frequency in Hz

Output voltage (Vo) in

Volts

Gain

(A=Vo/Vin)

Gain in dB

20 log(A)

RESULT:

EX NO: 8 DATE:

SINGLED TUNED AMPLIFIER

AIM:

(i)To construct and draw the frequency response of single tuned amplifier using

BJT for fo = -------------------

(ii) To find the bandwidth and quality factor

CIRCUIT DIAGRAM:

DESIGN(Tank circuit):

Given fo = ---------------

Assume C = 0.01uf

fo = 1/(2π√(LC))

L = 1/(4π2fo

2C)

MODEL GRAPH:

PROCEDURE:

1. Construct the circuit as shown in the Fig.

2. Set the input value in the millvolts range using AFO

3. Vary the frequency using the AFO and note the output Vo in the CRO.

4. By taking the frequency in X-axis and gain in Y-axis draw the graph.

5. Note the center frequency fo and calculate the quality factor.

TABULATION:

Vin =

RESULT:

S.No Frequency

in Hz

Amplitude of

the output

voltage

(Vo)

Gain

(A=Vo/Vin)

Gain in db

20log(A)

EX NO: 9 DATE:

COMPLEMENTRY SYMMETRY PUSH PULL AMPLIFIER

AIM:

To construct and draw the frequency response of complementry symmetry push

pull amplifier using BJT

CIRCUIT DIAGRAM:

MODEL GRAPH:

PROCEDURE:

1. Construct the circuit as shown in the Fig.

2. Set the input voltage using AFO

3. Vary the frequency using AFO and note the output across RLin the CRO.

4. By taking the frequency in X-axis and gain in Y-axis draw the graph.

5. Note the lower and upper cutoff frequency by drawing the 3db line

6. From these two frequencies calculate the band width.

TABULATION:

Vin =

RESULT:

S.No Frequency

in Hz

Amplitude of

the output

voltage

(Vo)

Gain

(A=Vo/Vin)

Gain in db

20log(A)

EX NO: 10 DATE:

AUDIO FREQUENCY OSCILLATOR

AIM:

(i)To construct an audio frequency oscillator using BJT for fo = ----------------------

-

(ii)To compare the theoretical frequency with the practical frequency

CIRCUIT DIAGRAM:

DESIGN(Bridge network):

Given fo = ----------------

Assume C = 0.01uf

fo = 1/(2πRC) , R4 = 2R3

where R1=R2=R and C1=C2=C

R = 1/(2πfoC)

Let R3 = ----------

R4 = 2R3

MODEL GRAPH:

PROCEDURE:

1. Give the connections as shown in the circuit diagram.

2. Switch on the supply and see the output sine wave in the CRO.

3. Note the peak to peak amplitude and one time period of the sine wave and draw the

waveform in the graph.

4. Compare the obtained frequency with the theoretically calculated frequency.

TABULATION:

No.of divisions

in the X axis

Time/div Total time

period(ms)

No.of divisions

in the Y axis

Volt/div Total

voltage(V)

Output

MODEL CALCULATION:

Obtained frequency fo =

Theoitical frequency =

RESULT:

EX NO: 11 DATE:

RELAXATION OSCILLATOR USING UJT

AIM:

To construct a relaxation oscillator using UJT for fo = -----------------------

CIRCUIT DIAGRAM:

MODEL GRAPH:

PROCEDURE:

1. Give the connections as shown in the circuit diagram.

2. Switch on the supply and observe the output across the capacitor in the CRO.

3. Note the valley point Vv, peak point Vp, time for one cycle and the shift.

Calculate the frequency.

4. Draw the graph between time versus voltage across the capacitor.

TABULATION:

No.of divisions

in the X axis

Time/div Total time

period(ms)

No.of divisions

in the Y axis

Volt/div Total

voltage(V)

Output

RESULT:

EX NO: 12 DATE:

CASCODE AMPLIFIER

AIM:

To construct and draw the frequency response of cascode amplifier

CIRCUIT DIAGRAM:

MODEL GRAPH:

PROCEDURE:

1. Construct the circuit as shown in the Figure.

2. Set the input voltage using AFO

3. Vary the frequency using AFO and note the output across, the collector terminal of

second transistor in the CRO.

4. By taking the frequency in X-axis and gain in Y-axis draw the graph.

5. Note the lower and upper cutoff frequency by drawing the 3db line from the mid band

gain.

6. From these two frequencies calculate the band width.

TABULATION:

Vin =

RESULT:

S.No Frequency

in Hz

Amplitude of

the output

voltage

(Vo)

Gain

(A=Vo/Vin)

Gain in db

20log(A)

Vs

100Ω

2KΩ 2KΩ

10KΩ

1KΩ

10KΩ

1KΩ

1µF 1µF

1µF

1KΩ

+VCC

+VDCVC

47µF