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1. DIODE CHARACTERISTICS
Aim: To study the diode characteristics under forward and reverse biased conditions.
(1) Junction Diode(2) Zener Diode
Equipment required:
Name of the equipment Range QuantityPower Supply (0 – 30) V 1 No
Ammeter (0 – 30) mA(0 – 100) µA
1 No1 No
Voltmeter (0 – 1) V(0 – 30) V
1 No1 No
Circuit: Forward Bias
Fig A
Circuit: Reverse Bias
Fig B
Procedure:
Forward Bias:
(i) Connect the circuit as per the circuit diagram.(ii) Vary the power supply voltage in such a way that the readings are taken in steps of
0.1 V in the voltmeter till the power supply shows 20V.(iii) Note down the corresponding ammeter readings.(iv) Plot the graph between V and I.
(v) Find the dynamic resistance .
Reverse Bias:
(i) Connect the circuit as per the circuit diagram.(ii) Vary the power supply voltage in steps of 1 V till the voltmeter reads 20V.(iii) Note down the corresponding ammeter readings.(iv) Plot the graph between V and I.
(v) Find the dynamic resistance .
Result: Forward and Reverse bias characteristics of Junction and Zener diodes are plotted and their dynamic resistance is as follows:
Dynamic resistance r Junction Diode Zener DiodeForward BiasReverse BiasModel Graph:
I (mA)
-I (µA)
V (V)-V (V)V1 V2
I1
I2
VB
VB : Break down Voltage
ΔV
ΔI
Testing of Diode:
Connect negative probe of the multimeter to the cathode and positive probe to the anode. The meter will not show any reading. Now inter change the connections. i.e. negative probe of the multimeter to the anode and positive probe to the cathode. The meter will show reading. If in both of these positions, the diode does not show any reading, then the diode is open and if in both these positions diode shows reading (of low resistance), then the diode is leaking. If in both these positions diode shows zero ohms, then the diode is short. If we take the voltage drop across the diode under forward based condition, it will show 0.6 to 0.7 V for a silicon diode and 0.2 to 0.3 V for a Germanium diode.
Review Questions:
1) For which substance the width of the forbidden band lies between a conductor and an insulator?
2) What is biasing?3) How does the temperature affect the breakdown voltage?4) What is volt equivalent of temperature VT? 5) What is diode resistance?
2. CLIPPING AND CLAMPING CIRCUITS
Aim: To observe the clipping waveform in different clipping configurations and to study the clamping circuits as (a) Positive clamping circuits (b) Negative clamping circuits
Equipment Required:
Equipment Range QuantitySignal Generator (0 – 1) MHz 1 No
Cathode Ray Oscilloscope (0 – 20) MHz 1 NoPower Supply (0 – 30) V 1 No
Circuit Diagram:
Clipping Circuits:
Clipping Circuits:
Fig 1. (a)
1KΩ
5 V1 KHz
0.7 V+
-
+
-2 V
VO
+
-
Fig 1. (b)
Fig 1. (c)
2 V
Fig 1. (d)
Fig 1. (e)
Fig 2. (a)
Fig 2. (b)
Fig 2. (c)
Fig 2. (d)
Clamping Circuits:
Procedure:
(1) Connect the circuits as per the circuit diagram.(2) Set the input signal voltage (say 5V, 1KHz) using signal generator.
C
R
(3) Observe the output waveforms using CRO operated in dc mode.(4) Sketch the observed waveform on the graph sheet.
Clamping Circuits:
Design equations:
Given f = 1KHz, T = τ = 1/f = 1X10-3 sec = RC
Assuming C = 0.1 µF; then R = 10 KΩ.
Procedure:
(1) Connect the circuits as per the circuit diagram.(2) Set the input signal voltage (say 5V, 1KHz) using signal generator.(3) Observe the output waveforms using CRO operated in dc mode.(4) Sketch the observed waveform on the graph sheet.
Review Questions:
1)What is a clipper or a limiter circuit?2)Which circuit is used for amplitude selection?3)What is a clamper circuit?4)What is the role of τ = RC time constant in clamper circuits?5)What is the difference between positive and negative clampers?
3. TRANSISTOR CHARACTERISTICS
Aim: To plot the transistor characteristics of a Common – Emitter configuration and to find the h – parameters to the same.
Equipment required:
Equipment Range QuantityPower Supply (dual channel) (0 – 30) V 1 No
Ammeter (0 – 10) mA and (0 – 1) mA 2 Nos (1 No each)Voltmeter (0 – 30) V and (0 – 2) V 2 Nos (1 No each)
Circuit Diagram:
Procedure:
Input characteristics:
(1) Connect the circuit as per the circuit diagram.(2) Set VCE = constant (say 5 V) and vary VBE in steps of 0.1V and note down the
corresponding IB. (3) Repeat the above procedure for VCE = 10 V, 15 V, etc…(4) Plot the graph between VBE and IB for constant VCE.(5) Find the h – parameters: (a) hfe : Forward Current Gain
(b) hie : Input impedance
Output characteristics:
(1) Connect the circuit as per the circuit diagram.(2) Set IB = constant (say 20 µA) and vary VCE in steps of 1V and note down the
corresponding IC. (3) Repeat the above procedure for IB = 40 µA, 60 µA, etc…(4) Plot the graph between VBE and IB for constant VCE.(5) Find the h – parameters: (a) hre : Reverse Voltage Gain
(b) hoe : Output admittance
Model Graph:
Input characteristics:
Output characteristics:
Tabular column:
Input characteristics: VCE = Constant
VBE (Volts) IB (µA)
VBE1 VBE2
IB2
IB1
VBE Volts
IB µA
VCE Volts
ICO
IB4
IB3
IB2
IB1
VCE = constant
IC mA
IC2
IC1
Output characteristics: IB = Constant
VCE (Volts) IC (mA)
Result:
Parameter Practical readingshfe
hie
hre
hoe
Review Questions:
1) What is the biasing condition for a transistor in active region?2) What are dependent and independent variables in BJT model?3) What is meant by a Bipolar Junction Transistor?4) What are the main features of selecting h – parameters for BJT modelling?5) What is base spreading resistance in BJT?
4. FET CHARACTERISTICS
Aim: To plot drain and transfer characteristics for the given FET and to find the drain resistance and trans-conductance.
Equipment required:
Equipment Range QuantityPower Supply (dual channel) (0 – 30) V 1 No
Ammeter (0 – 30) mA 1 NoVoltmeter (0 – 30) V 2 Nos
Circuit Diagram:
Procedure:
Drain Characteristics:
(1)Connect the circuit as per the circuit diagram.(2)Set the gate voltage VGS = constant (say -1 V) and vary the drain voltage VDS in steps of
1V and note down the corresponding drain current ID. (3)Repeat the above procedure for VGS = 0 V, +1 V, etc…(4)Plot the graph between VDS and ID for constant VGS.
(5)Find the drain resistance .
Transfer characteristics:
(1) Connect the circuit as per the circuit diagram.(2) Set the drain voltage VDS = constant (say +5 V) and vary the gate voltage VGS in steps
of 1V (negative voltage) and note down the corresponding drain current ID.
(0-30) V
+-
68KΩ
+-
+ -
+-
1KΩ(0-30) mA
(0-30) V
(0-30) V (0-30) V
BFW 10
(3) Repeat the above procedure for VDS = +10 V, +15 V, etc…(4) Plot the graph between VGS and ID for constant VDS.
(5) Find the trans-conductance .
Model Graph:
Drain Characteristics:
Transfer Characteristics:
Tabular column:
Drain characteristics: VGS = Constant
VDS (Volts) ID (mA)
ID mA
VDS V
ID2
ID1
VGS4
VGS3
VGS2
VGS1
VDS1 VDS2
VGS = constant
ID mA
ID2
ID1
VGS (Volts) VGS2 VGS1
VDS = Constant
Transfer Characteristics: VDS = Constant
VGS (Volts) ID (mA)
Result:
Parameter Practical readingsrD
gm
µ = rD x gm
Review Questions:
1) What are the distinguished characteristics of a FET over a BJT?2) What are the advantages and disadvantages of FET?3) Why it is FET called so?4) What is pinch – off voltage?5) What is Voltage Variable Resistance (VVR) in a FET?6) What is the main application of a VVR in a FET?
5. PHOTO DETECTOR
Aim: Study of photo Detector’s characteristics
1. Light dependent resistor
2. Photo diode
3. Photo Transistor
Equipment Required:
S. No Equipment Range Quantity
1.Power Supply
(Dual Channel)(0-30) V 1
2. Ammeter (0-10) mA 1
3. Voltmeter(0-10) V(0-30) V
2
Circuit Diagram:
Light Dependent Resistor:
Photo Diode:
(0-10) V(0-10) V
(0-30) V
(0-10) mA680 Ω
DC bulbLDR
1 KΩ
(0-30) V
(0-10) V (0-10) V (0-30) V
(0-100) µA680 Ω
DC bulb
1 KΩ
(0-30) V
Photo Transistor:
Procedure:
Light Dependent Resistor:
1. Connect the circuit as per the circuit diagram.
2. Maintain a known distance (say 5 cm) between the DC bulb and the LDR.
3. Vary the voltage of the bulb in steps of 1V and note down the resistance value across the LDR using multimeter.
4. Plot the graph: V vs R.
Photo Diode:
1. Connect the circuit as per the circuit diagram.
2. Maintain a known distance (say 5 cm) between the DC bulb and the Photo Diode.
3. Set the voltage of the bulb (say 2V), vary the voltage of the diode in steps of 1V and note down the corresponding diode current IT.
4. Repeat the above procedure for VL = 4V, 6V etc.
5. Plot the graph: VT vs IT for a constant VL.
Model Graph:
(0-10) V (0-10) V (0-30) V
(0-10) mA680 Ω
DC bulb
1 KΩ
(0-30) V
Photo Diode
Photo Transistor
Note: Repeat the Photo Diode experiment procedure for Photo Transistor also.
Review Questions:
1. What is the difference between Diode and Photo Diode?
2. What is meant by dark current in Photo Diode?
3. What is a Photo Transistor?
R (Ω)
V (Volts)IT
(µA)
VT (Volts)
V3V2V1
IT (mA)
VT (Volts)
V3V2V1
V4
Light Dependent Resistor
4. What is the working principal of LDR?
5. What is the roll of DC bulb in this experiment?
6. SELF BIAS BJT AMPLIFIER
Aim: To design and implement the self bias circuit amplifier and obtain
1. Bias Resistance 2. Measures of gain 3. Frequency response.
Equipment Required:
S. No Equipment Range Quantity
1. Power Supply (0-30) V 1
2. CRO (0-20) MHz 1
3. Function Generator (0-1) MHz 1
Design:
Given data: VCC = 15V, IC = 1 mA, hfe (obtain from multimeter or manual)
For active condition
Circuit Diagram:
Procedure:
1. Connect the circuit as per the circuit diagram.
2. Set Vs = 50 mV, using the signal generator.
3. Keeping the input voltage constant, vary the frequency from 0 to 1MHz in regular steps and note down the corresponding output voltage.
4. Plot the graph: gain (dB) vs. frequency.
5. Find the input and output impedances.
6. Calculate the bandwidth from the frequency graph.
Tabular Column:
Vs = 50 mV
S. No Frequency Vo (Volts) Gain = Vo/ Vi Gain (dB) = 20 log(Vo/ Vi)
VS = 50 mV
Freq = (0-1 ) MHz
+VCC
Model Graph:
Result:
Parameter Theoretical Practical
Gain(Mid band)
Bandwidth
Review Questions:
1. Define amplification?
2. What is biasing? Why it is necessary?
3. Mention the applications of CE amplifier, justify?
4. Universal biasing technique is preferred over any other biasing technique. Why?
7. SINGLE STAGE RC COUPLED AMPLIFIER
Aim: To design and implement the RC coupled amplifier circuit and to find
1. Cut-off frequencies 2. Band Width 3. Mid Band gain
4. Input/output impedance.
Equipment Required:
S. No Equipment Range Quantity
1. Power Supply (0-30) V 1
2. CRO (0-20) MHz 1
3. Function Generator (0-1) MHz 1
Design:
Given data: VCC = 15V, IC = 1 mA, fL = 100Hz, Stability factor = (0-10), hfe (obtain from multimeter or manual), AVS = 50 dB, IE = 1.2mA.
Gain formula is given by
Assuming,
Effective load resistance is given by RL eff = RC// RL
Emitter resistance is given by
Where, re is internal resistance of the transistor
On applying KVL to output loop, we get
VCC = ICRC + VCE + IERE
Where VE = IERE
Find RC =?
From equation, find RL =?
Since IB is very small when compared with IC.
IC = IE
VB = VBE + VE
Stability factor
Find RB =?
RB = RB1 // RB2
Find RB1 and RB2
Input impedance Zi = (RB // hie)
Output impedance Zo = RC // RL
Input coupling capacitance is given by
XCi = Zi / 10
Find Ci =?
Output coupling capacitance is given by
XCo = (RC // RL)/10
Find Co =?
By pass capacitance is given by
Find CE =?
Circuit:
Procedure:
1. Connect the circuit as per the circuit diagram.2. Set Vs = 50 mV, using the signal generator.3. Keeping the input voltage constant, vary the frequency from 0 to 1MHz in regular
steps and note down the corresponding output voltage.4. Plot the graph: gain (dB) vs. frequency.5. Find the input and output impedances.6. Calculate the bandwidth from the frequency graph.
VS = 50 mV
Freq = (0-1 ) MHz
RS
CCi
RB1
RB2
RC
RE
CCo
CE
RLV
i
Vo
+VCC
Tabular Column:
Vs = 50 mV
S. No Frequency Vo (Volts) Gain = Vo/ Vi Gain (dB) = 20 log(Vo/ Vi)
Model Graph:
Result:
Parameter Theoretical Practical
Input impedance Zi = RBB / hie
Output impedance Zo = RC // RL
Gain(Mid band)
Bandwidth
Review Questions:
1. Why is negative feedback used in RC Coupled amplifier?
2. Why 3dB line in gain calculations?
3. Mention applications of RC Coupled amplifier.
4. What is the phase angle in RC Coupled amplifier?
8. FET AMPLIFIER
Aim: To determine the parameters of the single stage JFET amplifier (Common Drain).
1. Band Width 2. Mid Band Gain 3. Input and Output impedances.
Equipment Required:
S. No Equipment Range Quantity
1. Power Supply (0-30) V 1
2. CRO (0-20) MHz 1
3. Function Generator (0-1) MHz 1
Design:
Given data: IDSS = 10mA; VP = -4V; fL = 50Hz; VDD = 12V; RS = 680Ω.
From the DC bias condition
For which
Find VGS =?
VDD = IDRD + VDS + VS
Since ID = IS (IG = 0)
Assume RS = 500Ω
Find RD =?
Find
The value of gm at the bias voltage is given by
Find gm =?
Find rm =?
With RS completely by passed the largest amplifier gain is given by
Find AV =?
For which RGS = open and RGS = 100MΩ
Input coupling capacitance is given by
XCi = RGS / 10
Find Ci =?
Output coupling capacitance is given by
XCO = (RD // RL) / 10
Find CO =?
By pass capacitor is given by
Find CS =?
Circuit:
Procedure:
1. Connect the circuit as per the circuit diagram.
2. Set Vs = 50mV, using the signal generator.
3. Keeping the input voltage constant, vary the frequency from 0 to 1MHz in regular steps and note down the corresponding output voltage.
4. Plot the graph: gain (dB) vs. frequency.
5. Find the input and output impedances.
6. Calculate the bandwidth from the frequency graph.
VS = 50mV
Freq = (0-1 ) MHz
R’S
Ci
RE
Co
RL
Vi
+VD
D
RG
S
CS
RD
RS
VO
Tabular Column:
Vs = 50mV
S. No Frequency Vo (Volts) Gain = Vo/ Vi Gain (dB) = 20 log(Vo/ Vi)
Model Graph:
Result:
Parameter Theoretical Practical
Input impedance
Output impedance
Gain(Mid band)
Bandwidth
Review Questions:
1. What are the advantages of FET amplifier over conventional transistor amplifier?
2. List out the applications of FET amplifier, justify?
3. What are the factors, which influence the higher cut- off frequency?
4. What components, which influence the lower cut-off frequency?
9. CASCODE AMPLIFIER
Aim: Design and test the cascode amplifier for the given specifications and find the following
1. Mid Band Gain 2. Input/output impedance
Equipment Required:
S. No Equipment Range Quantity
1. Power Supply (0-30) V 1
2. CRO (0-20) MHz 1
3. Function Generator (0-1) MHz 1
Design:
Given data:
VCC = 15V, fL = 1 KHz, S = (2-10), IE1 = IE2 = 1mA, RL = 4.7KΩ.
AVT = 100, β1 = β2 = 100, RS = 600Ω.
Assume
RL eff = Rc // RL
hie1 = β1 re1
β1 = β2
IE1 = IE2
re1 = re2
Gain is given by
With RL = re2 = hib2 of transistor 2 and
Total gain is given by
AVT = AV1AV2 = 100
Find AV2 =?
Calculate RC from RL eff = Rc // RL
On applying KVL to output loop, we get
VCC = ICRC + VCE1 + VCE2 + VE
Find RE =?
Since β1 = β2 = 100, IB1 = IB2
Assume R3 = 4.7KΩ, I3 = VB1 / R3
Find I3 =?
I2 = I3 + IB1
Find I2 =?
R2 = [VB2 – VB1] / I2
I1 = I2 + IB2
Find I1 =?
R1 = [VCC – VB2] / I1
Find R1 =?
Input coupling capacitance is given by
XC2 = (hie2 // RL // R3) / 10
Find C2 =?
XC1 = (hie1 // R1 // R2) / 10
Find C1 =?
Output coupling capacitance is given by
XCO = (RC // RL) / 10
Find CO =?
By pass capacitor is given by
Find CE =?
Circuit:
Procedure: 1. Connect the circuit as per the circuit diagram.2. Set Vs = 50mV, using the signal generator.3. Keeping the input voltage constant, vary the frequency from 0 to 1MHz in regular
steps and note down the corresponding output voltage.4. Plot the graph: gain (dB) vs. frequency.5. Find the input and output impedances.
VS = 50mV
Freq = (0-1 ) MHz
RS
CCi
R1
R2
RE
CCo
RL
Vi
+VCC
Q1
Q2
R3
CE
RC
C
I1
I2
I3
IB2
IB1
6. Calculate the bandwidth from the frequency graph.
Tabular Column:
Vs = 50mV
S. No Frequency Vo (Volts) Gain = Vo/ Vi Gain (dB) = 20 log(Vo/ Vi)
Model Graph:
Result:
Parameter Theoretical Practical
Input impedance
Output impedance
Gain(Mid band)
Bandwidth
Review Questions:
1. What is the difference between darlington pair and cascode amplifier?
2. What is the phase angle in darlington pair amplifier?
3. What is the phase angle in cascode amplifier?
4. List out the particular applications of darlington pair amplifier and cascode amplifier. Justify?
10. DARLINGTON PAIR (COMMON COLLECTOR AMPLIFIER)
Aim: Design and test a darlington current amplifier and find the following
2. Current Gain 2. Voltage Gain 3. Band Width 4. Input/output impedance
Equipment Required:
S. No Equipment Range Quantity
1. Power Supply (0-30) V 1
2. CRO (0-20) MHz 1
3. Function Generator (0-1) MHz 1
Design:
Given data:
VCC = 12V, fL = 50Hz, S = (0-10), IE = 1mA, RL = 1KΩ.
AV ≤ 1, AI = AI1 * AI2
Since hfe1 = hfe2,
AI = (hfe) 2
From DC bias analysis, on applying KVL to the output loop, we get
VCC = VCE + IERE,
,
RE eff =?
VE = IERE eff,
RE eff = RE // RL,
Find RE =?
Find RB =?
RB = R1 // R2
VB = VBE + VE
Find R1 & R2 =?
Zi1 = 2 hie + (1+ hfe1) RE
Find Zi1 =?
Zieff = Zi1 // RBB
Zo = RE // [((RS // RB) + 2 hie)/ (hfe) 2]
Find Zo =?
Find Ci =?
Find CE =?
Circuit:
Procedure:
1. Connect the circuit as per the circuit diagram.
2. Set Vs = 1 V, using the signal generator.
3. Keeping the input voltage constant, vary the frequency from 0 to 1MHz in regular steps and note down the corresponding output voltage.
4. Plot the graph: gain (dB) vs. frequency.
5. Find the input and output impedances.
6. Calculate the bandwidth from the frequency graph.
Tabular Column:
Vs = 1 V
S. No Frequency Vo (Volts) Gain = Vo/ Vi Gain (dB) = 20 log(Vo/ Vi)
Model Graph:
VS = 1 V
Freq = (0-1 ) MHz
RS
CCi
R1
R2 R
E
CC
o
RL
Vi
Vo
+VC
C
Q1
Q2
Result:
Parameter Theoretical Practical
Input impedance
Output impedance
Gain(Mid band)
Bandwidth