I-yearExperiments

Department of Physics & Electronics,

LM College of Science & Technology, Jodhpur

Experiments for Practical Work

1. Design and study of constant voltage source

2. Maximum Power transfer form source to load using

resistive circuit

3. Design and study of constant current source

4. Characteristics of triode

5. Semiconductor Diode Characteristics

6. Photocell Characteristics

7. Frequency response of series resonance circuits

8. Frequency response of parallel resonance circuits

9. DIAC characteristics

10. Zener Diode Characteristics

11. Voltage regulation by Zener Diode

12. FET Characteristics

13. Transistor characteristics in CB mode

14. Transistor Characteristics in CE Mode

15. Single Stage BJT amplifier


LM College of Science & Technology, Jodhpur.

CONSTANT VOLTAGE SOURCE

Experiment No.1

Object: To Study and design of a constant voltage source.

Apparatus used: Two resistance boxes, connecting wires, Digital multi-meter (DMM) as voltmeter and DC regulated power supply.

Formula Used: A voltage source, which produces a constant terminal (load) voltage, is called constant voltage source. A practical voltage source consists of a voltage source in series with a resistance Rs. The terminal voltage across the load is given by

where,

VL = voltage across the resistance, RL in volt.

RL = load resistance in .

Rs = source resistance in .

V = applied voltage in volt.

When RL >> RS, the load voltage, VL remains almost constant and equal to V.

[Constant voltage source] Page 1 of 4



Circuit Diagram:

Experimental set-up for constant voltage source

Graph:

Procedure:




1. Set up the given circuit as shown in circuit diagram.

2. Take the value of source resistance Rs constant say 500Ω.

3. Take the upper terminal A as positive with respect to terminal B.

4. Now change the value of load resistance in steps of 500Ω from 500Ω to 10,000Ω.

5. Note the corresponding voltage VL, for each changed value of RL.

6. Find out the current value IL for every value of RL.

7. Plot the graph by taking load resistance RL on the X-axis and VL on the Y-axis.

Observations:

(i) Applied Voltage (ii) Source resistance

Observation table -

S. No. RL ΩTerminal voltage

VL (volt)Load Current

1.2.3.4.

050010001500

.

.

.10000




Result: The V-I curve and a plot between load resistance and load voltage are shown on the graph. From the graph we find that when RL >> Rs, then we obtain constant voltage across load resistance RL.




MAXIMUM POWER TRANFER

Experiment No. 02

Object: Study of a maximum power transfer from source to load, using resistive circuit.

Apparatus used: Two resistance boxes, DC regulated power supply, Digital multi-meter (DMM) as voltmeter and connecting wires.

Formula used: Power delivered to the load terminals

where ,

Vs = the applied input voltage in volt.

Rs = fixed source resistance in Ω.

PL = transferred power PL to load resistance in watt.

VL = voltage across RL in volt.

RL = variable load Resistance in Ω.

[Maximum power transfer] Page 1 of 4



Circuit diagram:

Experimental set-up for maximum power transfer theorem

Graph:




Procedure:

1. Set up the given circuit as shown in circuit diagram.

2. Set the source resistance at a constant value at 500Ω.

3. Now change the value of load resistance in small steps say 50Ω starting from 50Ω and note down the corresponding value of voltage VL across the load terminal for each value changed of RL.

4. Find out the power for the each changed value of load resistance.

5. Plot the curve for power by taking, load resistance on X-axis and note the value of load resistance for obtained maximum power.

Observations:

(i) Applied Voltage (ii) Source resistance

Observation table -

S. No. RL Ω Terminal voltageVL (volt)

Power

(mW)

1.2.3.4.

050

100150

.

.

.1000




Result: The plot of load resistance (RL) versus power PL is shown in the graph. From graph we find that for RS = RL, maximum power is transferred from source to load, when RL = _____ (= Rs) Ω.

Maximum power transferred = _____mW.




CONSTANT CURRENT SOURCE

Experiment No. 03

Object: To design and study of a constant current source.

Apparatus used: Digital multi-meter (DMM) as milli-ammeter, two resistance boxes, connecting wires and DC regulated power supply.

Formula used: A source, which supplied a constant current to a load, is known as a constant current source. The load current is given by

where,

RL = load Resistance in Ω.

IL = current through load RL in A.

Rs = fixed source resistance in Ω.

Is = source current in A.

The above equation shows that when RL<< RS i.e. smaller is the ratio RL/RS, the load current (IL) remain almost equal to IS.

Circuit Diagram:

[Constant current source] Page 1 of 4



Experimental set-up for constant current source

Graph:




Procedure:

1. Set up the given circuit as shown in the circuit diagram.

2. Set the source resistance to a constant value at 10000Ω and apply the constant dc voltage 10 volt by the dc power supply.

3. Case-I when RL<< RS

(i) Change the value of load resistance RL in small steps say 50Ω from 50Ω to 1000 Ω.

(ii) Note down the current flowing in the circuit by the DMM using as the milli-ammeter.

(iii) Calculate the load voltage VL for each value of load resistance RL.

4. CASE II, when RL ≤ RS

(i) For this case change the value of load resistance with steps of 500Ω and note down the current value in the circuit by DMM for every value of RL.

(ii) Calculate the load voltage VL for each value of RL.

5. For both the cases plot the graph for load current by taking RL on X-axis and IL on Y-axis.

Observations:

(i) Source Resistance(ii) Applied Voltage

Observation tables –

1. CASE-I, when RL<< RS

S. No. RL in ohms Load currentIL in volts

Voltage across load

1.2.3.4.

50100150

.

.

.




1000

2. CASE-II, when RL ≤ RS

S. No. RL in ohms Load currentIL in volts

Voltage across load

1.2.3.4.

50100150

.

.

.1000

Result: The plot between load resistance (RL) and load current (IL) for the current source is shown in the graph. From the curves we find that when RL<< RS the load current IL

is constant.




CHARACTRISTICS OF TRIODE

Experiment No. 04

Object: To study the characteristic of a triode and calculate the various parameters (μ, gm, rp ) of triode.

Apparatus used: Experimental kit and connecting wires.

Formula used: There are two important triode characteristics: the plate characteristics and the transfer (or mutual) characteristics. The plate characteristic is a graph between plate voltage Vp and plate current Ip for a fixed value of grid voltage Vg. From this characteristic, the plate dynamic resistance can be calculated by using the following definition:

and plate static Resistance

The variation of plate current Ip with grid voltage Vg for fixed value of VP is plotted in mutual (or transfer) characteristics. The transconductance gm can be determined as

The amplification factor µ can be determined with the help of the formula

[Characteristics of Triode] Page 1 of 6



Circuit Diagram:

Experimental set-up for triode characteristics

Graphs:




Procedure:

To obtain plate and mutual characteristics of a given triode:

1. To plot the plate characteristics

(i) Assemble the circuit as shown in circuit diagram.

(ii) Plug the main lead to the mains carrying 220V, 50Hz A.C.

(iii) Put the power ON/OFF switch to the ON position and ensure that light is glowing.

(iv) Adjust the grid voltage at desired value (eg. -1, -2, etc.)

(v) Note down in the Observations table the plate current IP, for various value of VP starting from 0 to a maximum value of 250 volt.

(vi) Obtain different sets of Observationss for different grid voltage say -1,-2,-3,…-5. Thus a family of plate characteristics curve may be plotted as shown in fig.

Note : Don’t exceed grid voltage above +2V, because tube may be damaged.

2. To plot mutual characteristics

(i) Adjust the plate voltage VP to a suitable value, say 80V

3. Note the plate current IP as grid voltage Vg is varied through suitable steps of 0.5 volts starting form 0 volt to such a negative value at which IP becomes zero. Again obtain different set of Observations for different value of VP, say 20V, 80V, 120V, 160V. Thus a family of mutual characteristics curve may be platted as shown fig.

4. To determine the co-efficient (rp, gm) and µ of the triode from its characteristics.




(i) Plate Resistance (rp)

From the plate characteristics of triode, calculate the

of the curve for any fixed grid voltage.

Thus .

(ii) Trans conductance (gm)

From the mutual characteristics curve of triode calculate

the slope for any constant plate voltage

Thus .

(iii) Amplification factor µ

can be calculated by multiplying rp and gm.

Observations:

1. Plate Characteristics

S.No. Plate Voltage Plate current

1.2.3.4.

0102030....

250




2. Mutual characteristic

S.No. Grid voltage Plate current

1.2.3.4.

0-0.5-1

-1.5...

Calculations:

1). From Plate characteristics Vg = _____volt.

VP = _____ volt, IP = _____mA

(i) Static Resistance

(ii)

Dynamic Resistance

2). From mutual Characteristics

Vp= _____

(iii)

3). Then _____.

Result: The plate characteristic and mutual characteristic of the triode are shown in graph. The triode parameters are as follows –

Parameter Value




RP

rp

gm mS




FORWARD CHARACTERISTICS OF SEMICONDUCTOR DIODE

Experiment No. 5

Object: To Study characteristics of p-n Junction diode and determine the forward static and dynamic resistance.

Apparatus used: Experimental board, Digital multi-meter (DMM) as milli-ammeter, dc voltmeter, power supply and connecting wires.

Formula Used: At a given operating point we can determine the static resistance and dynamic resistance of the diode from its characteristic. The static resistance is defined as the ratio of the dc voltage to DC current, i.e.

,where V and I are the voltage and current

at any point.

The dynamic resistance is the ratio of a small change in voltage to a small change in current, i.e.

in Ω

[Forward characteristics of semiconductor diode] Page 1 of 4



Circuit Diagram:

Experimental set-up for semiconductor Diode characteristics

Graph:

Procedure:

1. Trace the given circuit and using the suitable patch cords make the connection for one diode.

2. Connect the DMM as milli ammeter and voltmeter of suitable range (0-3) V.

3. Switch on the power supply. Now change the input voltage with a small step and increases the voltage slowly.




4. Note the milli-ammeter and voltmeter readings for each setting of the input voltage in the Observations table.

5. Draw the graph between voltage and current.

6. For the linear part of the curve, calculate the static and dynamic resistance of the diode as shown in fig.

7. Take the other diode in the circuit and repeat the above.

Observations:

V-I characteristics-

S. No.

Diode - D1 Diode - D2 Diode - D3

Voltage

(V)

Current

(mA)

Voltage

(V)

Current

(mA)

Voltage

(V)

Current

(mA)1.2.3.

00.10.20.3

.

.

.

.

00.10.20.3

00.10.20.3




Calculations:

From Graph - For diode – D1, D2 and D3

1). V = _____volt, I = _____mA

Static resistance

2).

Dynamic resistance

Results: The V-I characteristics of the diodes are shown in the graph. The values of static and dynamic resistance of different diodes are as given below:

Diode Rd rd

D1

D2

D3

ΩΩ

ΩΩΩ




PHOTO CELL

Experiment No. 6

Object: To study the characteristics of a photocell and verify the inverse square law.

Apparatus used: Optical Bench with two stands and meter scale, photocell (Selenium), two light sources (bulb), micro-ammeter (0-50 µA), voltmeter, connecting wires.

Formula used: The photocell generates a voltage across a circuit element under illumination. The photo electric current I, at a distance d is directly proportional to intensity of illumination and

where, I = photo current in µA

d = distance between photocell and light source in cm.

P = illuminating power of a source.

Hence if two sources with illuminating power P1 and P2 causes the same current I at distances d1 and d2 respectively, then we have

[Photo cell] Page 1 of 4



Circuit Diagram:

Experimental set-up for photocell characteristics




Graph:

Procedure:

Arrange the optical bench in such a way that both the lamp no. 1 and the photo cell are at the same level.

1. Make the connections of the photo cell to Micrometer. Red socket to positive and black socket to negative terminal of the µA.

2. Adjust the distance of the lamp in such a way that when it is connected to mains and light is allowed to fall on the sensitive portion of the cell and get a little deflection in the µA.

3. Now increase or decrease the distance as the current deflection changes by the step of 5 deflections for the bulb-1.

4. Then the repeat the same Observationss for the bulb-2.

5. A graph between reading (I) and for both the bulbs is separately drawn on the same graph paper, by taking current I on the Y-axis.




Observations:

S. No.

For bulb-1 [25 W] For bulb-2 [15 W]

Current

(µA)

Distance of bulb from cell

(d)(cm.)

Current

(µA)

Distance of bulb from cell

(d)(cm.)

1.2.3.

051015...

50

051015...

50

Result: The plot for I versus for both the bulbs are shown on the graph, which is a straight line, it shows that photo current, I i.e. micro ammeter reading is inversely proportional to the square of distance from the source i.e. d, thus inverse square law is verified.




SERIES RESONANCE CIRCUIT

Experiment No.7

Object: To Study the resonance in a series LCR circuit and determine its resonance frequency, also calculate the quality factor Q of the coil.

Apparatus used: Experiment board containing coils, capacitors and resistors, AC voltmeter, signal generator and connecting wires.

Formula used: At series resonance frequency, the inductive reactance is equal to capacitive reactance and the current is maximum. The resonant frequency of series resonant circuit is -

where L = inductance in Henry

C = capacitance in Farad

At resonance frequency

Quality factor of coil

where,

fr = resonance frequency in Hz

RL= load resistance in ohms

[Series resonance] Page 1 of 6



Circuit Diagram:

Experimental set-up for series resonance

Graph:




Procedure:1. Set up a series circuit consisting of the resistance (R) an

inductor (L) and a capacitor (C) as shown in the circuit diagram. The value of L and C should be chosen to produce resonance at a frequency about the middle of the desired frequency range.

2. Connect the A.C. milli-voltmeter in parallel across the resistor (across terminals A and B)

3. Supply a constant a.c. voltage from the function generator.4. With the resistant set at some value say 510Ω and voltage

applied to the circuit maintained constant, increase the signal frequency in steps from a convenient low value, until the desired resonance frequency is covered.

5. At each step, note the frequency and the voltage and also calculate the value of the current for chosen resistor value.Note: In the vicinity of resonance, take reading a sufficient no. of frequencies (i.e. the frequency steps should be small) to assure resonance.

6. Plot the graph for current with frequency along the x-axis and current in the y-axis. Find the resonance frequency at which maximum value of current Imax is obtained.

7. Now calculate the value and find the two corresponding

frequencies and calculate the bandwidth.8. Repeat the experiment with some other value of resistor R.

Observations:

(i) Inductance L = _____H (ii) Capacitance C = _____F (iii) Applied Input voltage VI = 3 volts.




Observation tables-

S. No.

Frequency

f (Hz)

Load Resistance

R1 = _____Ω

Load Resistance

R2 = ____Ω

Voltage across

resistance

(V)

Current Voltage across

resistance (V)

Current

1.

2.

3.

1000

1500

2000

.

.

10000

Calculations: From the resonant curve-

(a).R = 510

Cut off frequencies f1 = _____Hz, f2 = _____Hz

(b).R = 1000

Cut off frequencies f1 = _____Hz, f2 = _____Hz

1. The theoretical value of resonant frequency

fr (Th) = _____ HZ

2. The Quality factor of the circuit

(a). for R = R1= _____ Ω,

(b). for R = R2 = _____Ω,

From resonant curve-




3. Practical value of resonant frequency

4. Practical values of Quality factor

(a). for R = R1 _____ Ω and R2 = ______ Ω

Cut off frequencies

Band width

Quality factor

(b). for R = R2 = _____ Ω

Cut off frequencies

Band width




Result: Frequency response curve for series resonant circuit is shown on graph.

The theoretical and practical values of resonant frequency and Quality factor as obtained are-

Theoretical

Practical

fr

Q1 (RL = 510Ω)

Q2 (RL = 1000Ω)

Hz Hz




PARALLEL RESONANCE CIRCUIT

Experiment No. 8

Object: To Study the resonance in a parallel LCR Circuit and determine its resonant frequency.

Apparatus used: Experiment board containing coils, capacitors and resistors, AC voltmeter, signal generator and connecting wires.

Formula Used: The resonance frequency of a parallel resonant circuit is given by

In the parallel resonant circuit, the current is minimum in the circuit at resonance frequency, since the impedance becomes very high.

Procedure:

1. Set up a parallel combination of a coil and a condenser, with the resistance in series of the coil.

2. Use suitable value of ‘L’ and ‘C’ find the theoretical resonance frequency.

3. Connect the A.C. milli-voltmeter across the parallel circuit.

4. Apply the signal from signal generator to circuit, maintained constant voltage at a suitable value say 3V.

5. Vary the frequency with a small interval, until the minimum voltage is obtained. In the vicinity of resonance, the frequency steps should be small.

6. At each step note, the frequency, the voltage across load resistance and also calculate the line current.

7. Plot the graph for current with frequency along the x-axis and current on the y-axis. Find the resonance frequency at which minimum value of current Imin is obtained.

[Parallel resonance] Page 1 of 4



8. Repeat the experiment with other value of resistor R.

Circuit Diagram:

Experimental set-up for parallel resonance




Graph:

Observations:

Inductance (L) = _____H

Capacitance (C) = _____F

Applied Input voltage VI = 3Volts




Observation tables-

S. No.

Frequency

f (Hz)

Load Resistance

R1 =____ Ω

Load Resistance

R2 = ____Ω

Voltage across

resistance (mV)

Current Voltage across

resistance (mV)

Current

1.

2.

3.

1000

1500

2000

2500

.

.

10000

Calculations: The theoretical value of resonance frequency

From resonance curve

Practical resonance frequency .

Result: The frequency versus line current curve is shown on the graph paper. The practical and theoretical values of resonance frequency are obtained as fallows;

,




DIAC CHARATERISTICS

Experiment No. 9

Object: To study the characteristic of DIAC.

Apparatus used: Experimental kit, voltmeter (0-50V), Digital multi-meter (DMM) as a milli-ammeter and connecting wires.

Theory: The DIAC is a two terminal device (MT1 and MT2). It is a parallel inverse combination of semiconductor layers, which can pass current in either direction when the breakdown voltage is reached in either polarity across the two terminals.

Procedure:

1. Connect the DMM, DIAC, voltmeter to the circuit.

2. Make the MT1 terminal positive and MT2 terminal negative.

3. Switch ON the power supply.

4. Increase supply voltage in steps, note the corresponding currents and voltages for each step.

5. Plot the graph for V-I characteristics.

6. Reverse the terminals of DIAC. Again increase supply voltage in steps, note the corresponding currents and voltages in step.

7. Plot the V-I characteristics for negative voltage and current.

Note: - The V-I characteristics in forward and reverse is divided into two regions.

(a). For applied positive voltage less than breakdown voltage (VBO) a small leakage current flows through the device and DIAC blocks the flow of current.

(b). When the applied voltage is equal to or greater than the breakdown voltage, DIAC begins to conduct and voltage drop across it becomes a few volts. At this point, avalanche breakdown occurs for the reverse biased junction and the device exhibits –ve resistance i.e. current through the device increases with decreasing values of applied voltage.

[Characteristics of DIAC] Page 1 of 5



Circuit Diagram:

Experimental set-up for diac characteristics




Graph:




Observations:

CASE I: when applied voltage makes MT1 positive with respect to MT2

S. No.

Bias Voltage

V (volt)

Current IT

(mA)

1.

2.

3.

4.

0

5

10

.

.

30

31

32

.

.




CASE II: when applied voltage makes MT1 negative with respect to MT2

S.No. Bias voltage

V (volt)

Current IT

(mA)

1.

2.

3.

0

5

10

.

.

30

31

32

Result: The V-I characteristics of DIAC is plotted on the graph.

The breakdown voltage the DIAC turns on and current through the DIAC increases rapidly. The breakdown voltage is same in both directions of conduction and is equal to = _____ volt.




CARACTERISTICS OF ZENER DIODE

Experiment No. 10

Object: Study of characteristics of Zener diode under the reverse-biased conditions and calculate the static and dynamic resistance.

Apparatus used: Experimental board, Digital multi-meter (DMM) as a milli-ammeter, voltmeter (0-10V), Connecting wires and dc power supply.

Formula Used: A P-N junction diode normally does not conduct when it is reverse biased. But if the reverse bias is increased, at a particular voltage it starts conducting. This voltage is called break down voltage.

The static resistance of the diode is given by

The dynamic resistance of the diode is given by

where, ΔV = change in voltage (when conducting)

and ΔI = change in current

[Characteristics of Zener diode] Page 1 of 4



Circuit Diagram:

Experimental set-up for zener diode characteristics

Graph:




Procedure:

1. Set up the circuit as shown in circuit diagram. Connect DMM as milli-ammeter and voltmeter of suitable range.

2. To study reverse characteristics, the positive of the battery is connected to the N-side and negative of the battery is connected o the P-side of the diode.

3. Switch on the power supply. Increase slowly the supply voltage in steps of 1 V starting from 0V. Each time measure the input voltage Vi, VZ and current IZ.

4. When the break down occurs for the increased value of the Vi, the VZ remains almost constant but the value of current IZ

increases.

5. Plot the characteristic curve by taking voltage VZ on the negative X-axis and current IZ on the negative y-axis.

6. Calculate the reverse breakdown voltage and dynamic resistance of diode in the breakdown region from the graph.

Observations:

V-I characteristics:

S. No. Supply VoltageVI(volts)

Voltage across zener diode

Vz (volts)

Current through zener diode

Iz (mA)1.2.3.

0123...

30




Calculation:

From the graph-

1. Breakdown voltage =_____V

2. Static resistance

3. Dynamic resistance

Result: The V-I characteristics of zener diode is shown in the graph. From the graph

(i). Zener break down voltage VZ = _____ volt

(ii). The static resistance of the diode Rs = _____

(iii). The dynamic resistance of the diode rd = _____




VOLTAGE REGULATION BY ZENER DIODE

Experiment No. 11

Object: To study of the voltage regulation using zener diode

Apparatus used: Experimental Board with zener diode, resistance box, DC power supply of (0-30V), Digital multi-meter (DMM) as a voltmeter and connecting wires.

Formula Used: The zener diode works as a shunt regulator, the zener diode operates in the reverse breakdown region. The limiting resistor R is given by

(Design formula)

where,

Vin = d.c. input voltage in volts,

Vout (=Vz) = output voltage across load resistance RL in volts.

Procedure:

1. Connect the zener diode shunt regulator circuit as shown in circuit diagram.

2. Case-I Input line regulation

(i) Set load resistance R at a fixed value says 1000Ω.

(ii) Increase the input voltage Vin with a step of 1V and note the resultant output voltage Vout.

(iii) Plot the graph for output voltage Vout by taking Vin on X-axis and Vout on Y-axis. Find the minimum input voltage after that the Vout obtained constant.

3. Case-II Load regulation

(i) Set input voltage Vin at a fixed value says 10 V.

[Voltage regulation by of Zener diode] Page 1 of 4



(ii) Increase the value of load resistance R with a step of 200Ω and note the resultant output voltage Vout for each value of R.

(iii) Plot the graph for output voltage Vout by taking R on X-axis and Vout on Y-axis. Find the minimum value of R after which the Vout obtained constant.

Circuit Diagram:

Experimental set-up for voltage regulation by zener diode

Observations:

1. Variation of output voltage with input voltage, keeping load resistance R =1000 Ω constant-

S. No. Input Voltage

Vin (volt)

Output Voltage

Vout (volt)

1.

2.

3.

4.

0

1

2

3

.




.

30

2. Variation of output voltage with load resistance, keeping input voltage Vin constant-

Input voltage Vin = 10 volt

S. No. Load Resistance

RL (ohm)

Load Voltage

Vout (volt)

1.

2.

3.

4.

200

400

600

.

.

.

1000




Calculations:

1. From the graph 1-

The break down voltage of zener diode i.e. the minimum value of input voltage for which Vout becomes constant = _____ volt

2. From the graph 2-

The minimum of load resistance RL, for which output voltage Vout becomes constant = ______ .

Graph:

Result: The plots for the output voltage versus input voltage and output voltage versus load resistance are shown on the graphs.

From graph regulated output voltage is obtained for

(i). minimum value of load resistance RL (min) = ______

(ii). minimum value of input voltage Vin = ______volt.




FET CHARACTERISTICS

Experiment No. 12

Object: To study the Field effect transistor (FET) characteristics, and plot the drain and mutual characteristics, also calculate the FET parameters.

Apparatus used: Experimental board, Dual dc power supply, Digital multi-meter (DMM) as a milli-ammeter, dc voltmeters (0-3v) and (0-10V) and connecting wires.

Formula used: FET is a three terminal device (source, gate and drain), it is a uni- polar device. The gate is given a negative bias with respect to the source. The drain is given positive potential with respect to the source. The important parameter of FET are defined as

1. Static Resistance

2. Drain dynamic resistance

where, VDS is the drain-to-source voltage,

ID is the drain current,

VGS is the gate voltage.

3. Mutual conductance

4. Amplification factor

[JFET characteristics] Page 1 of 5



Circuit Diagram:

Experimental set-up for JFET characteristics

Graph:




Procedure:

1. Trace the given circuit.

2. Make the circuit connection as shown in circuit diagram by using DMM as a milli-ammeter and voltmeter of suitable range.

3. To plot drain characteristics

(i) First, fix VGS at some value, say 0V, Increase the drain voltage VDS slowly in steps of 1 volt. Note drain current ID

for each step.

(ii) Now, change VGS to another value and repeat the above. Take reading for 3 to 4 gate voltage value.

(iii) Plot the drain characteristics i.e. graph between VDS and ID for the fixed values of VGS.

4. To plot mutual characteristics

(i) Fix the drain voltage VDS to a suitable value say 1V.

(ii) Now, increase the negative grid voltage VGS slowly in step of 0.2V until the current ID becomes zero.

(iii) Take the different set of Observations of grid voltage and drain current for different constant value of VDS.

(iv) Plot the curve between grid voltage VGS and drain current ID for the fixed value of VDS.

5. Find the FET parameters from the characteristics.

Observations:

1. Drain characteristics –




S. No. VDS (volt)Drain current ID (mA)

VGS = 0V VGS = -1V VGS = -2V

1.2.3.

012..

10

2. Mutual characteristics-

S. No.

VDS =_____V VDS = _____V VDS=_____ V

VGS (V) ID (mA) VGS (V) ID (mA) VGS (V) ID (mA)

1.

2.

3.

0-0.1-0.2-0.3

.

.

3V




Calculations:

1. From the drain characteristics -

(i). At VGS =_____volt

(ii). small change in drain voltage = _____volt

small change in drain current = _____mA

2. From the mutual characteristics Drain voltage

(i). ,

3. Amplification factor

Result: The drain characteristics of the FET are plotted on the graph.

The parameters of FET determined from the drain characteristics are given below:

Parameter value determined

rd

gm

k

mS




TRANSISTOR CHARACTERISTICS (COMMON-BASE)

Experiment No. 13

Object: To study the transistor characteristics in the common-base mode and calculate the input / output static and dynamic resistance and current gain.

Apparatus used: Experimental kit, power supply and connecting wires.

Formula used: A transistor is a three terminal active device. The three terminals are emitter, base and collector. The input static resistance is given by

The input characteristic is a plot between IE and VEB keeping voltage VCB constant. The input dynamic resistance is calculated using the formula-

The output characteristic curves are plotted between IC and VCB

keeping IE constant. The output dynamic resistance is very high (almost ∞). The output static resistance is-

The dc and ac current gains (alpha) are defined as follows-

dc current gain,

ac current gain,

[Transistor characteristics (CB)] Page 1 of 6



Circuit Diagram:

Experimental set-up for common base configuration

Graph:




Procedure:

1. To plot the Input characteristics:

(i) Using suitable patch cords make connection as per in circuit diagram for a PNP transistor.

(ii) Keep the knobs of both the 0-10V DC supplies to fully anticlockwise position.

(iii) Switch ON the mains supply.

(iv) Set the collector voltage a certain value say 1 volt.

(v) Vary the emitter voltage in steps of say 0.1 volt starting from zero and note down the corresponding values of the emitter current.

(vi) Repeat the whole process for some another values of collector voltage.

(vii) Plot the readings on a graph paper. Take emitter voltage on the X-axis and emitter current on Y-axis.

2. To plot the output characteristics

For the output characteristics of a transistor in common base configuration the emitter current is kept constant at a certain value.

(i) Keep the knobs of both the 0-10V D.C. supplies to fully anticlockwise position.

(ii) Switch ON the mains supply.

(iii) Set emitter current to a certain, value say 1mA.

(iv) Reverse the polarity of the voltmeter connected across the (0-10) V supply in the output circuit.

(v) Note the voltage corresponding to point ‘0’V.

(vi) Now increase the collector voltage till the collector current becomes zero.

(vii) Now revert back the polarity of the voltmeter across the collector supply.

(viii)Vary the collector voltage in steps of say 1 volt and observe the corresponding collector current.

(ix) Plot the collector current versus collector voltage reaching on a graph sheet for different constant values of emitter current.




3. Find the different parameters as defined above from the characteristics curves.

Observations:

(i) Input characteristics-

S. No.VCB = 1V VCB = 4V VCB = 7V

VEB (mV) IE (mA) VEB (mV) IE (mA) VEB (mV) IE (mA)

1.2.3.

0.50.520.540.560.58

.

.1.0




(ii) Output characteristics-

S. No.

IE = 1mA IE = 3mA IE = 5mA

VCB (V) IC (mA) VCB (V) IC (mA) VCB (V) IC (mA)

1.

2.

3.

-0.7

0

1

2

3

.

.

Calculations:

4. From the input characteristics.

(i) Input static resistance

(ii) Input dynamic resistance

ΔVEB = _____ volt,




5. From the output characteristics Output static Resistance =

,

Output static resistance Ro =

6. DC current gain

7. AC current gain -

Result: The characteristics of the transistor in common base mode is shown in the graphs. The transistor parameters are given below.

Parameter Value

Rs (input)

rd (input)

Ro (output)




TRANSISTOR CHARACTERISTICS (COMMON-EMITTER)

Experiment No. 14

Object: To Study the transistor characteristics in common-emitter mode and calculate the input and output dynamic resistance with the current gain.

Apparatus used: Experimental kit, power supply and connecting wires.

Formula used: In CE configuration, we make the emitter terminal common to the input and output. For CE configuration, we defined the important parameters as follows:

1. Input static resistance

2. Input dynamic resistance

3. Output static resistance

4. Output dynamic resistance

5. DC current gain

6. AC current gain

[Transistor characteristics (CE)] Page 1 of 6



Circuit Diagram:

Experimental set-up for common Emitter configuration

Graph:




Procedure:

1. To plot input characteristics

(i) Using suitable patch cords make connections as per in circuit diagram for PNP transistor.

(ii) Keep the knobs of both 0-10 V D.C. supplies to fully anticlockwise position.

(iii) Switch on the power to the kit board.

(iv) Set the collector voltage to certain value say 1 volts.

(v) Vary the base voltage VBE in 0.02V steps and observe the corresponding base current by keep the current meter in (0-200) µA range.

(vi) Repeat the base voltage and base current readings for different sets of the collector voltage.

(vii) Plot the readings on graph sheet. Take VBE on the X-axis and IB on the Y-axis.

2. To plot output characteristics

For obtaining the output characteristics the base current in kept fixed at certain value.

(i) Keep the knobs of both 0-10V DC voltage suppliers to fully anticlockwise position.

(ii) Set the base current to a certain value say 10mA with the help of (0-1) V D.C. supply of the input circuit.

(iii) Now vary the collector voltage from 0 to 10 volt in steps of say 1 volt and note down the corresponding values of collector current.

(iv) Repeat the collector voltage and collector current readings for different settings of the base current.

(v) Plot a graph of collector voltage along X-axis and collector current along Y-axis.

Note: For each new value of collector voltage check the base current. It should be adjusted to the value set in the step (ii).

Observations:

1. Input Characteristics –




S. No.VCB = 1V VCB = 4V VCB = 7V

VBE (V) IB ( ) VBE (V) IB ( ) VBE (V) IB ( )

1.2.3.

0.40.50.520.540.56

.

.

.

.




2. Output characteristics -

S. No.IB = 20 IB = 40 IB = 60

VCE(V) IC (mA) VCE(V) IC (mA) VCE(V) IC (mA)

1.2.3.

0.40.812..

10

Calculations:

1. From the input curves-

(i) Input static resistance

(ii) Input dynamic resistance

,




2. From the output characteristics

,

(i) Output static resistance

(ii) Output dynamic resistance

3. DC current gain

4. AC current gain

, , .

Result: Input and output characteristics are plotted on the graph. The parameters of the transistor in CE mode are given below:

Parameter Value determined

Rs (input)

rd (input)

ro(output)

βdc

βac




SINGLE STAGE TRANSISTOR AMPLIFIER

Experiment No. 15

Object: Study of a single stage amplifier and to draw frequency response curve of a common emitter RC coupled amplifier and determine the bandwidth.

Apparatus used: DC voltage supply, experimental kit of common emitter RC coupled, function generator, AC milli-voltmeter and connecting wires.

Formula used: The output voltage is much more than input voltage, the circuit works as an amplifier circuit. The voltage gain of this amplifier is given by the formula-

The bandwidth of the amplifier is given by

Bandwidth (BW) = f2-f1 in Hz.

where, f2 = upper cut off frequency in Hz.

f1= lower cut off frequency in Hz.

at which the voltage gain reduces to 0.707 times from its maximum value.

Procedure:

1. Trace the given circuit of the single stage transistor amplifier.

2. Connect the dc supply VCC and measure the dc voltage supplied.

3. Connect the signal generator at input terminals and ac voltmeter at the output terminals.

4. Now feed a low voltage (10mV) ac signal at the input such that the output wave shape gets not distorted.

5. Set the signal generator frequency to the very low frequency says 50Hz. Measure the output voltage and find the voltage gain.

[Single stage Transistor CE amplifier] Page 1 of 4



6. Keeping the signal voltage fixed, change the frequency of signal. For each frequency measure the output voltage and calculate the voltage gain in the Observations table.

7. Plot the response curve on a semi log graph paper. Find the lower and upper cut-off frequencies from the curve and calculate the bandwidth.

Circuit Diagram:

Experimental set-up for Single stage transistor amplifier




Observations:

1. Applied bias voltage = -10 volt,

2. Input voltage

S. No.

Frequency

(Hz)

Output Voltage

Vo (volts)

Voltage Gain

1.2.3.

5060..

100200

.

.

.1K (1000)

2K...

10 K20 K

.

.100K200K

.

.1000k(1M)




Calculations: From graph.

1. Maximum value of gain Amax = _____

2. _____

f1 = _____Hz, f2 =_____Hz

Bandwidth = Δf = f2 - f1 = ______ Hz

Result: The frequency response curve of common emitter single stage amplifier is shown on the graph.

1. The maximum value of gain of the amplifier Amax = _____

2. Bandwidth (BW) = _____Hz

Graph:


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