Analog Electronics Lab Manual Experiment No 6-11

Experiment No. 6

Objective

Design of Simple Amplifier Circuit (Common Emitter)

Objectives

1.       To design a common emitter transistor (NPN) amplifier circuit.

2.       To obtain the frequency response curve of the amplifier and to determine the Mid-frequency gain, A mid, lower and higher cutoff frequency of the amplifier circuit.

Apparatus Required

Sl.no	Name of components	Rating /Ranging	Quantity
1	Transistor:
2	Resistors:
3	Capacitors:
4	Power Supply
5	Oscilloscope
6	Function Generator
7	Breadboard
8	Connecting wire

Design:

Before designing the circuit, one needs to know the circuit requirement or specifications. The circuit is normally biased for V_CE at the mid-point of load line with a specified collector current. Also, one needs to know the value of supply voltage V_CC and the range of β for the transistor being used (available in the datasheet of the transistor).

Here the following specifications are used to design the amplifier:

V_CC = 12V and I_C = 1 mA

Start by making V_E= 0.1 V_CC.

Then R_E = V_E/I_E (Use I_E≈I_C).

Since V_CE = 0.5 V_CC,

Voltage across R_C = 0.4V_CC,  i.e. R_C = 4.R_E

In order that the approximation analysis can be applied, R₂≤0.1βR_E .

Here β is the minimum rated value in the specified range provided by the datasheet (in this case β =50).

Finally, R₁=V1 R₂ ,   V₁ =( V_CC-V₂) and V₂ (= V_E+V_BE) are voltages across R₁ and R₂,respectively.

Based on these guidelines the components are estimated and the nearest commercially available values are used.

Procedure:

1.       Measure and record all the values of resistance and capacitance and β of the transistor using a multimeter. Configure the circuit as per the diagram.

2.       Apply supply voltage to the circuit. Measure and record all the dc parameters listed in table 1 in absence of the ac signal.

Circuit diagram:

Space for Design:

OBSERVATIONS:

Table 1

D.C. analysis of the circuit:  VCC = 12V
Parameter	Computed value	Observed value
VB (V)
VE (V)
IC ≈ IE (mA)
VCE (V)
Q-point is at (……….V,…………mA

Conclusion:

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….…………………………………………………………………………………………………………………………………………………..

Viva Questions

1. What do you mean by Transistor?
2. What are the types of Transistor?
3. Why it is called Bipolar?
4. What do you mean by Bipolar and Unipolar?
5. Explain briefly NPN & PNP transistor.
6. What is the voltage gain of CE mode?
7. What is voltage gain?
8. What is current gain?
9. What is the relationship between voltage and current gain?
10. What is the relationship between current in base, collector &emitter junction?
11. What is the current gain in CB mode?
12. What are the materials used for preparing transistor?
13. Is there any phase inversion in CB & CC mode?
14. Is there any phase inversion in CE mode?
15. What is the Input impedance in CB, CC, and CE mode?
16. What is the Output impedance in CB, CC, and CE mode?
17. In which mode power gain is more?
18. What are h-parameters?
19. Explain each h-parameter calculation with the help of I/P & O/P characteristics?
20. What are the typical values of h-parameters?
21. What is meant by quiescent operating point?
22. How should quiescent operating point be located to get distortion less amplification?
23. What is the need of biasing a transistor?
24. Distinguish b/w DC load line & AC load line on collector characteristics?
25. Define h-parameters of a two-port network?
26. What are biasing combination in a transistor?
27. What is DC current gain & base transport factor?

Space for Notes:

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Experiment No. 7

Object

                RC coupled single stage FET/BJT amplifier and determination of gain Frequency Response.

Objectives

        To design and setup an RC Coupled amplifier using BJT to determination of gain Frequency Response.

Apparatus Required

Sl.No	Name	Range	Quantity
1	Transistor
2	Capacitor
3	Resistors
4	Signal Generator
5	CRO

Circuit diagram:

Space for Design:

.

Procedure:

1.          Measure and record all the values of resistance and capacitance and β of the transistor using a multimeter. Configure the circuit as per the diagram.

2.          Apply supply voltage to the circuit. Measure and record all the dc parameters listed in table 1 in absence of the ac signal.

3.       Next, set the function generator in 20hz “frequency” range.  Also,  set  the

“Attenuation” button at 40db. Connect the output to the oscilloscope and adjust the “amplitude” knob till you get a sinusoidal input signal, vi ≈ 100-200 mv peak-to-peak value. Do not change this setting throughout the experiment.

4.       Now apply this input signal to the circuit you have made keeping the connection to oscilloscope in tact. Feed the output of the circuit to the other channel of oscilloscope. Take care to make all the ground pins common.

5.       With input signal amplitude always constant, increase signal frequency slowly. Observe measure and record the output voltage, v_o. Scan the entire frequency in the range 20 hz – 2 mhz. You may have to measure v_i and take the ratio v_o/v_i each time in case input fluctuation is too large to hold constant.

6.       Calculate the voltage gain for each frequency. Observe the inverted output.

7.       Plot the frequency response curve, i.e. Voltage gain in db versus frequency on a semi-log graph-sheet.

8.       Estimate the mid-frequency gain and also the lower and higher cut off frequencies and hence the bandwidth.

Waveform:

TABULAR COLUMN:

Sl. No.	Frequency, f (kHz)	V0(pp) (Volt)	Gain, AV = Vo( pp) Vi( pp)	Gain (dB) 20log(vo/vi)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34

Conclusion:

……………………………………………………………………………………………………………………………………………………….......……………………………………………………………………………………………………………………………………………………….......……………………………………………………………………………………………………………………………………………………….......……………………………………………………………………………………………………………………………………………………….......

Viva Questions

1. Define amplifier? What are different types of amplifiers?
2. Classification of amplifier based on principle of operation?
3. Which amplifier is having maximum efficiency? Minimum distortion?
4. Where class-A amplifier is used?
5. What is the necessity of studying the frequency response cure?
6. What causes non-linear distortion in an amplifier?
7. How do you reduce lower 3-dB frequency in an RC coupled CE amplifier?
8. How much phase shift is introduced in single stage RC coupled amplifier?
9. Why do you prefer to express gain in dB?
10. How do you calculating the bandwidth in amplifier circuit?
11. What is the significance of the coupling capacitance and emitter bye-pass capacitance?
12. What are the applications of RC coupled amplifier?
13. Why cut-off frequency is called half power frequency?
14. What is quality (Q) factor? How it is related to bandwidth? What is its significance?
15. What are the various types of distortion in amplifier?
16. The best frequency response is of ---------------- coupling (R-C, transformer, direct).
17. What is the gain of an emitter follower circuit?
18. What is the type of feedback used in Emitter follower circuit?
19. Why Emitter follower circuit is used?
20. What is ‘Q’ point?
21. How do you calculate current gain in emitter follower circuit?
22. What is impedance matching?
23. What is the bandwidth of emitter follower in comparison with CE amplifier?
24. Why the circuit is called emitter follower?

Experiment No. 8

Object

                Op-Amp as Inverting and Non Inverting Amplifier

Objectives

                To construct and test the performance of an Inverting, Non-inverting amplifier using IC μA 741

Equipment / Components:

S. No.	Name	Range	Quantity
1	Dual Power Supply
2	Resistors
3	Regulated Power Supply
4	IC μA 741
5	Voltmeter
6	Connecting Wires

Theory:

INVERTING AMPLIFIER:

                The fundamental component of any analog computer is the operational amplifier or op-amp and the frequency configuration in which it is used as an inverting amplifier. An input voltage Vin is applied to the input voltage. It receives and inverts its polarity producing an output voltage. this same output voltage is also applied to a feedback resistor Rf, which is connected to the amplifier input analog with R1. The amplifier itself has a very high voltage gain.

If Rf = R1 then Vo=Vi

NON- INVERTING AMPLIFIER:

                Although the standard op-amp configuration is as an inverting amplifier, there are some applications where such inversion is not wanted. However, we cannot just switch the inverting and non inverting inputs to the amplifier itself. We will still need negative feedback to control the working gain of the circuit .Therefore, we will need to leave the resistor structure around the op-amp intact and swap the input and ground connections to the overall circuit.

VO/VI = (Rf / Ri) +1

From the calculations, we can see that the effective voltage gain of the non-inverting amplifier is set by the resistance ratio. Thus, if the two resistors are equal value, then the gain will be 2 rather than 1.

Design:

INVERTING AMPLIFIER:

Let A = -5; R1 = 1KΩ

A = − Rf / R1

Rf= 5 KΩ

Rcomp = R1 Rf / R1 + Rf=833 Ω

NON-INVERTING AMPLIFIER:

Let A = 6; R1 = 1KΩ

A = 1 + (Rf / R1)

Rf= 5 KΩ

Rcomp = R1 Rf / R1 + Rf= 833 Ω

PIN DIAGRAM:

Circuit Diagram: Inverting Amplifier:

Waveform:

Circuit Diagram: Non-Inverting Amplifier

Waveform:

PROCEDURE:

1.          Connections are made as per the EXPERIMENTAL SETUP.

2.          The supply is switched ON.

3.          Output is connected to anyone channel of CRO.

4.          The V1 and V2 voltages are fixed and measured from the other channel of CRO and the corresponding output voltages are also noted from the CRO.

5.          The above step is repeated for various values of V1 and V2.

6.          V1 and V2 may be AC or DC voltages from function generator or DC power supply.

7.          Readings are tabulated and gain was calculated and composed with designed values.

TABULATION:

Inverting Amplifier:

Sl. No	Input Voltage (in volts)	Output Voltage (in volts)
1
2

     Non- Inverting Amplifier:

Sl. No	Input Voltage (in volts)	Output Voltage (in volts)
1
2

Conclusion:

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Viva Questions

Q1. What is the significance of a differential amplifier?

Ans. The differential amplifier is capable of amplifying dc as well as ac input signals.

Q2. What are the applications of a differential amplifier?

Ans. In instrumentation systems

Q3. What is the meaning of CMRR?

Ans. It is the ratio of the differential voltage gain Ad to the common mode voltage gain A_cm.

Q4. What is the unit of CMRR?

Ans. Decibels (dB)

Q5. What is the value of CMRR for the 742 IC

Ans. 90 dB

Q6. what is the gain of the inverting amplifier in terms of resistances?

Ans. Gain (- Rf/Ri)

Q7. what is the gain of the non- inverting amplifier in terms of resistances?

Ans. Gain = (1+Rf/Ri)

Q8. what is the condition for averaging amplifier?

Ans. Rf/Ri =1/n, where n is no. of inputs applied.

Q9. What is the effect of –ve feedback on the voltage gain of an amplifier?

Ans. Increases the stability of its voltage gain.

Q10. What is meaning of gain of an amplifier with feedback?

Ans. Closed loop voltage gain

Experiment No. 9

Object

                Op-Amp as Summing Amplifier and Difference Amplifier

Objectives

                To construct and test the performance of an Summing Amplifier and Difference Amplifier using IC μA 741

Equipment / Components:

S. No.	Name	Range	Quantity
1	Dual Power Supply
2	Resistors
3	Regulated Power Supply
4	IC μA 741
5	Voltmeter
6	Connecting Wires

Theory:

SUMMING AMPLIFIER:

Summing amplifier is a circuit whose output is the sum of several input signals. For example: An inverting summing amplifier with two input voltages V1 and V2 two input resistors

R1 and R2 and a feedback resistor (consider all are of equal values).

DIFFERENTIAL AMPLIFIER:

                A circuit that amplifies the difference between two signals is called as a differential amplifier. This type of amplifiers is very useful in instrumentation circuits. From the experimental setup of a differential amplifier, the voltage at the output of the operational amplifier is zero. The inverting and non-inverting terminals are at the same potential. Such a circuit is very useful in detecting very small differences in signals. Since the gain can be chosen to be very large. For example, if R2=100R1, then a small difference V1-V2 is amplified 100 times.

The differential amplifiers amplify the difference between two voltages making this type of

Operational amplifier circuit a Subtractor unlike a summing amplifier which adds or sums together the input voltages. This type of operational amplifier circuit is commonly known as a Differential Amplifier configuration. By connecting each input in turn to 0v ground we can use superposition to solve for the output voltage Vout. Then the transfer function for a Differential Amplifier circuit is given as:

When resistors, R1 = R2 and R3 = R4 the above transfer function for the differential amplifier can be simplified to the following expression:

If all the resistors are all of the same ohmic value, that is: R1 = R2 = R3 = R4 then the circuit will become a Unity Gain Differential Amplifier and the voltage gain of the amplifier will be exactly one or unity. Then the output expression would simply be Vout = V2 - V1. Also note that if input V1 is higher than input V2 the output voltage sum will be negative, and if V2 is higher than V1, the output voltage sum will be positive.

The Differential Amplifier circuit is a very useful op-amp circuit and by adding more resistors in parallel with the input resistors R1 and R3, the resultant circuit can be made to either “Add” or “Subtract” the voltages applied to their respective inputs. One of the most common ways of doing this is to connect a “Resistive Bridge” commonly called a Wheatstone Bridge

Circuit Diagram: Summing Amplifier

Design:

Procedure:

1.       Connect the relevant circuit for the summing configuration as shown in the circuit diagram.

2.       Measure the output voltage Vo from AD Kit.

3.       Observe the waveforms at V1, V2, and Vo.

4.       Note the phase of the output voltage Vo with respect to the input voltage.

5.       Set different values of two input voltages, and find the output voltage

6.       Repeat the steps 3, 4, and 5.

7.       The waveforms are to be plotted.

Tabular Column:

Sl. No	Vin	Vout	Vout/Vin

 Circuit diagram: differential amplifier:

Design:

Differential Amplifier:

PROCEDURE:

1. Connect the relevant circuit for the difference configuration as shown in the circuit diagram.

2. Measure the output voltage Vo from AD Kit.

3. Observe the waveforms at V1, V2, and Vo.

4. Note the phase of the output voltage Vo with respect to the input voltage.

5. Set different values of two input voltages, and find the output voltage

6. Repeat the steps 3, 4, and 5.

7. The waveforms are to be plotted.

Tabular Column:

Sl. No	Vin	Vout	Vout/Vin

Conclusion:

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Viva Questions

Q1. What is adder?

Ans. Adder is that circuit which adds the magnitude of input signals.

Q2. What is scaling amplifier?

Ans. Scaling amplifier is that circuit in which each i/p is amplified by a weighted differently at the o/p and values of resistors are different.

Q3. What is average amplifier?

Ans. Average amplifier is that circuit in which each output is equal to the average of all the input voltage and the gain by which each input is amplified must be equal to 1 over the number of inputs.

Q4. What is the subtractor?

Ans. Subtract or is that circuit which subtracts the magnitude of input signals.

Q5. What is the use of offset minimizing resistor Rom?

Ans. To reduce the effect of i/p bias current on the o/p offset o/p.

Q6. What is gain of the inverting amplifier?

Ans. AF= - Rf / Ri

Q7. What are the applications of subtractor?

Ans. Computer, calculators, microprocessor.

Q8. what is the use of offset null compensating network in the adder?

Ans. To improves the accuracy of the adder.

Q9. What is the gain of an inverting amplifier?

Ans. Output voltage is equal to the –ve of ratio of feedback and i/p resistance.

Q10. What are the applications of adder?

Ans. Computer, calculators, microprocessor. LAB

Experiment No. 10

Object:

Op-Amp as, Integrator, Differentiator & Voltage Follower,

Objectives:

                To construct and test the performance of an Integrator, Differentiator & voltage follower using, IC μA741

Equipment / Components:

Sl. No.	Name	Range	Quantity
1	Dual Power Supply
2	Resistors
3	Regulated Power Supply
4	IC μA 741
5	AFO
6	Capacitor
7.	CRO
8.	Connecting Wires

Theory:

INTEGRATOR:

                One of the simplest of the operational amplifier that contains capacitor is differential amplifier. As the suggests, the circuit performs the mathematical operation of differentiation. The output is the derivative of the given input signal voltage. The minus sign indicates a 180⁰ phase shift of the output waveform Vo with respect to the input signal.

It is a low pass RC filter circuit. It can work as an integrator when time constant is very large. This requires very large values of R and C by Millers theorem the effective input capacitance becomes C!(1-Av)where Av is the gain of the op-amp. The gain Av is infinite for an ideal op-amp.so, the effect ive time constant of the op-amp becomes large which results in perfect integration. The output voltage of an integrator is shown below

DIFFERENTIATOR:

                Op-amps allow us to make nearly perfect integrators such as the practical integrator the circuit incorporates a large resistor in parallel with the feedback capacitor. This is necessary because real op-amps have a small current flowing at their input terminals called the "bias current". This current is typically a few nanoamps, and is neglected in many circuits where the currents of interest are in the microamp to milliamp range. The feedback resistor gives a path for the bias current to flow. The effect of the resistor on the response is negligible at all but the lowest frequencies.

It consists of an high pass RC filter .it acts as a differentiator for low values of time constant. Here the output is the derivative of the input signal by

Thus output is not only the derivative of the input but also out of phase by 180o with respect to the input.

Design:

INTEGRATOR:

Let fb= 50 Hz; Cf= 0.1μF

fb= 1 / 6.28 R1 Cf

R1 = 10KΩ

Rf= 10R1

Rf= 100 KΩ

DIFFERENTIATOR:

Let fa= 50 Hz; C1 = 0.1μF

fa= 1 / 6.28 RfC1

Rf= 31.8KΩ

Rf= 10R1

R1 = 3.1 KΩ

Circuit Diagram: Integrator                                                   

Waveform:

 Procedure:

1.          Connect the circuit as shown in the circuit diagram.

2.           Suitable Rf and C1 are chosen such that the output of the circuit is the integral of the input voltage.

3.          Apply square wave or sine wave input voltage (V) or any other type of signal at the input terminal.

4.          Observe the output voltage waveform on the CRO and note down the corresponding values.

5.          The time constant RfC1 is changed by changing the values of Rf or C1 and the corresponding output waveforms are noted.

Tabular Column:

Sl. No	Vin	Vout	Vout/Vin

Circuit Diagram: Differentiator                                                 

Waveform:

Procedure:

1.       Connect the circuit as shown in the circuit diagram.

2.       Suitable values of R1, R2, C1, C2 are chosen such that the output of the circuit is the integral of the input voltage.

3.        A square wave input voltage (V) is applied at the input terminal.

4.       Observe the output voltage waveform on the CRO and note down the corresponding values.

5.       The time constant R2C1 is changed by changing the values of R2 or C1 and the corresponding output waveforms are noted.

Tabular Column:

Sl. No	Vin	Vout	Vout/Vin

Conclusion:

…………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….…

Viva Questions

Q1.What is the differentiator?

Ans. The differentiator is that circuit in which o/p waveforms is the derivative of the input waveforms.

Q2. What is non-linear wave shaping?

Ans. Non-linear wave shaping is the process on applying any wave at input of a non- linear device, the shape of the output waves varies non-linearly with the input wave.

Q3. Give the application of a differentiator?

Ans. It is used in wave shaping circuits to detect high frequency components in an input signal and also as a rate of change of detector in F.M modulation.

Q4. What is the significance of input capacitor in a differentiator?

Ans. Input capacitor in a differentiator combines with feedback resister, selects lower cut off frequency.

Q5. When input of a differentiator is sine wave, then what is the output of the

Differentiator ?

Ans. Cosine wave.

Q6. What is the condition of differentiator for proper operating?

 Ans. T > Rf C1.

Q7. When input of a differentiator is square wave, then what is the output of a differentiator?

Ans. Spikes waves

Q8. Give the examples of linear circuits.

Ans. Adder, Subtractor, Integrator, Differentiator

Q9. When a number of stages are connected in parallel, the overall gain is the product of the individual stage gains.

Ans. False statement

Q10. A filter that provides a constant output from dc up to a cutoff frequency and passes no signal above that frequency is called a filter.

Ans. Low-pass

Q11. What is the integrator?

Ans. The integrator is that circuit in which output voltage is equal to the –ve of integral of input voltage.

Q12. What is the input offset voltage?

Ans. Input offset voltage is the error voltage that occurs at the i/p of op-amp, which causes to produce o/p offset voltages.

Q13. Why we use capacitor Cf in feedback loops of the integrator?

Ans. The feedback capacitor Cf combine with Rf is used to select cut off voltage.

Q14. What is the relation between input and output voltage?

Ans. Output voltage Vo is equal to the –ve of integral of input voltage.

Q15. If input of the integrator is sine wave, then which type of waveforms will obtain at the output of the integrator?

Ans. Cosine wave

Q16. What is the effect of resistor Rf that is connected across the feedback capacitor Cf in practical integrator? 

Ans. The feedback resistor Rf that remove the high frequency noise signals.

Q17. If input of the integrator is d.c. voltage, then which type of waveforms will be obtained at the output of the integrator?

Ans.  Ramp waveforms.

Q18. If input of the integrator is square wave , then, which type of waveforms will be obtain at the output of the integrator.

Ans. Triangular waveforms

Q19. What are the applications of an integrator?

Ans. It is used in analog computer, ADC, signal wave shaping circuits.

Q20. What is the effect of input bias current?

Ans. Input bias current produces output offset voltage at the output of an op-amp.

Space for notes:

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……………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………………………………………………………………………………….……………………………………………………………………………………………………………………………………………………

 Experiment No. 11

Object:

Design and implement a RC phase shift oscillator

Objectives:

To Design and implement a RC phase shift oscillator

Equipment / Components:

Sl. No.	Name	Range	Quantity
1	Dual Power Supply
2	Resistors
3	Capacitors
4	Transistor
5	Regulated Power Supply
6	Capacitor
7.	CRO
8.	Connecting Wires

Theory:

               

RC phase shift oscillator the feedback network consists of three identical RC sections. Each section produces a phase shift of 60^o therefore the net phase shift of the feedback is 180 ^o.  The amplifier stage introduces a phase shift of 180 ^o Therefore, the total phase shift between the input and output is 360 ^o or 0 ^o. When the circuit is energized, by switching on the supply, the circuit starts oscillating. The oscillations will be maintained if the loop gain is at least equal to unity. Feedback fraction of the RC phase shift network

b =1/29.

The frequency of oscillation  

f₀=1/2 πRCÖ6

Circuit diagram:

Space for design:

Procedure:

1. Connections are made as shown in the circuit diagram

 2. The DC power supply is switched ON

3. The output waveform is displayed on the CRO

4. The peak to peak amplitude and time period of the sine wave is noted

5. The graph of output waveform is drawn.

Conclusion:

Thus a RC phase shift oscillator is designed, constructed and tested.

Oscillator	Theoretical frequency	Practical frequency
RC Phase shift

Viva questions:

1) Give the condition which determines the frequency of oscillation

2) How clap oscillator can be constructed from colpitts oscillator?

3) Sketch a diode amplitude stabilization circuit for a wein bridge oscillator and explain its operation

4) Explain the phase-shift principle in Lc oscillators?

5) Compare and contrast RC & LC oscillators

6) Where do you use IC oscillators?