QUESTION BANK

Q. Part A
No. (Multiple Choice Questions)
Unit 1 CIRCUIT CONFIGURATION FOR LINEAR ICs

PART B
Define an operational amplifier.
An operational amplifier (commonly called an op-amp) is a high-gain, direct-coupled electronic voltage amplifier with a
differential input and usually a single-ended output. It amplifies the voltage difference between its two input terminals—
inverting (-) and non-inverting (+).
1. Key Features:
 High Input Impedance: Minimizes current draw from the signal source.
 Low Output Impedance: Allows it to drive heavy loads.
 Very High Gain: Open-loop gain can be over 100,000.
 Differential Input: Output depends on the voltage difference between the two inputs.

Compare the characteristics of an ideal and practical operational amplifier.

2.

3. Draw the circuit diagram of a differential amplifier and write its output voltage equation.

4. A 100 pF capacitor has a maximum charging current of 150 microamps. What is the slew rate?
 Design an amplifier with a gain of 10 and input resistance of 10 kΩ.

5.

What is meant by virtual ground of an op-amp?

Virtual ground refers to a point in a circuit that is maintained at 0 V (ground potential) without being
6. physically connected to ground.
In an ideal op-amp with negative feedback, the voltage difference between the inverting (-) and non-inverting
(+) inputs is zero. So, if the non-inverting input is at 0 V, the inverting input is also at 0 V — this is the virtual
ground.
Define CMRR

7.

List any four non-ideal DC characteristics of OP-AMP

 Input Offset Voltage
8.
 Input Bias Current
 Input Offset Current
 Drift (Temperature dependency of offset voltage and bias current)
What is the input offset voltage in the DC characteristics of an operational amplifier?
Input Offset Voltage is the differential DC voltage that must be applied between the input terminals of an op-
9.
amp to make the output zero (when ideally, it should already be zero with equal inputs).
It represents internal imbalances in the input stage of the op-amp.

10. State the significance of the input bias current in the DC characteristics of IC 741.
Input Bias Current is the average of the DC currents flowing into the inverting and non-inverting terminals
of the op-amp.
 In IC 741, it is typically in the range of tens to hundreds of nA.
Significance:
 It can cause voltage drops across external resistors connected to the inputs, leading to offset errors in
the output.
 It must be considered when designing precision analog circuits, especially in high-impedance
applications.

Define the term "output offset voltage" in the DC characteristics of an op-amp.

11.
Output offset voltage is the DC voltage present at the output of an op-amp when both inputs are grounded
(0 V). It results from internal mismatches and imperfections in the op-amp’s input stage.
How the input bias current affects the performance of an operational amplifier?
Input bias current, which flows into the op-amp input terminals, creates voltage drops across external
12.
resistors, leading to output offset errors.
In high-impedance circuits, this effect is more pronounced and can affect precision and accuracy of signal
amplification.
What is the closed-loop gain of a non-inverting amplifier?

13.

State the equation for the output voltage of an inverting amplifier with negative feedback.

14.

What is the effect of negative feedback in a closed-loop configuration of an op-amp?

Negative feedback:
 Stabilizes the gain
 Reduces distortion
15.
 Improves bandwidth
 Reduces sensitivity to parameter variations
 Improves linearity
 Controls the output impedance

For a non-inverting amplifier with a feedback resistor Rf=10kΩ and input resistor Rin=5kΩ, calculate the closed-
loop gain.
16.

In a closed-loop inverting amplifier, if the input voltage is 2V, Rf=20 kΩ, and Rin=10 kΩ, calculate the output
voltage.
17.

Given two input signals V1=2V and V2=1V, and feedback resistors Rf=10 kΩ and Rin=5 kΩ, calculate the
output voltage of a differential amplifier.

18.

19. For a differential amplifier gain of 10, if V1=3 V, V2=1 V, and the resistors are Rf=20 kΩ and Rin=10 kΩ,
calculate the output voltage.
 What is the main function of a differential amplifier?
20. The main function of a differential amplifier is to amplify the voltage difference between two
input signals while rejecting any common-mode signals (e.g., noise or interference present on both
inputs).
PART B
Mention some of the linear applications of op – amps.

1.
2

Find the output voltage of the following circuit. Given R1 =R2 = 10kΩ and Rf = 100 kΩ

2.
2

3.
Draw an adder circuit using op-amp to get the output expression as Vo = -(0.1V1 +V2 +5V3) 2
4. Draw the output voltage of adder-subtractor using op-amp.
2
How an op-amp can be used as a voltage follower?
An op-amp is configured with the output connected directly to the inverting input, and the signal applied to
5. the non-inverting input.
2
 Gain = 1
 Provides high input impedance and low output impedance

List the features of Instrumentation amplifier.

 High input impedance
 High CMRR
6.
 Low output impedance 2
 Excellent linearity
 High gain accuracy
 Low noise and drift
List the applications I-V and V-I converters.
 I-V (Current-to-Voltage) Converter:
 Photodiode amplifiers
7.  Sensor signal conditioning
2
 V-I (Voltage-to-Current) Converter:
 LED driving
 Analog actuator control
 Transducer excitation
What are the limitations of the basic differentiator circuit?
 Noise amplification (especially high-frequency)
8.
 Instability 2
 Sensitive to small signal variations
 Requires compensation or design improvements for practical use
9. Summarize an op-amp integrator. Mention its application. 2
 An integrator provides output proportional to the integral of the input signal.
 Applications:
 Signal wave shaping (e.g., square to triangle)
 Analog computation
  Low-pass filtering
Draw the circuit diagram of an integrator and give its output equation.

10.
2

11. Draw the circuit diagram of differentiator using Op-amp.

2
What is comparator?
12.
A comparator is a circuit that compares two voltages and outputs either HIGH or LOW depending on which 2
input is greater.
Differentiate a basic comparator and the Schmitt trigger.

13.
2

Make use of UTP and LTP in Schmitt trigger and tell how we can adjust hysteresis range.
 UTP (Upper Threshold Point): Input voltage at which output switches from LOW to HIGH
14.  LTP (Lower Threshold Point): Voltage at which output switches from HIGH to LOW
2
 Hysteresis = UTP - LTP
Adjust hysteresis by changing feedback resistor values in the Schmitt trigger circuit.

15. Draw the circuit of peak detector with its output waveform for a varying input signal
2
16.
Mention the conditions to be satisfied for sustained oscillation 2
Define Clipper.
17.
A clipper is a circuit that limits the output voltage to a specified level by clipping off portions of the 2
waveform without distorting the remaining part.
Define positive clamper and infer the application of it in electronic applications
18.
A positive clamper shifts the entire waveform upward so the negative peaks touch zero. 2
Application: Shifting signal baselines in communication and TV receivers.
What is filter? Mention some commonly used active filters.
A filter allows certain frequency components of a signal to pass while attenuating others.
Common active filters:
19.
 Low-pass 2
 High-pass
 Band-pass
 Band-stop (notch)
20.
Draw the circuit diagram of first order active low pass filter with its output waveform 2

Q. Part A
No. (Multiple Choice Questions)
PART B
1. What is analog multiplier?

2. How do you convert a basic multiplier to a squaring and square root circuit?

3. List the basic building blocks of PLL

4. What are the three stages through which PLL operates?

5. Define lock-in range of a PLL.

6. Define capture range of PLL.

7. Define pull-in time

8.
List the applications of 565 Phase Locked Loop.
9.
Define Voltage to Frequency conversion factor.
10. For perfect lock, what should be the phase relation between the incoming signal and VCO
output signal?
11.
What is a voltage-controlled oscillator?
12.
What is the purpose of having a low pass filter in PLL?
13.
Discuss the effect of having large capture range.
14.
VCO is called v-f converter? why?
15. What is the function of phase detector in PLL?

16.
Draw the relation between the capture ranges and lock range in a PLL.
17. What is lock range and capture range of PLL?

18.
Give the expression for the VCO free running frequency.
19. Derive the voltage output equation of the divider IC based square root circuit.

20.
Make use of Analog multiplier IC, develop the Squarer circuit.
 PART B
1. List the broad classification of Analog to Digital Converters

2. Summarize the disadvantages of flash type ADC

3. An 8-bit DAC has an output voltage range of 0-2.55 V. Solve for resolution.

4. Find the number of comparators required for realizing a 4‐bit flash ADC

5. Illustrate the working of sample and hold circuit with its circuit diagram and output waveform
6. Where are the successive approximation type ADC's used?

7. Mention the advantages of dual slope ADC.

8.
Define conversion time.
9.
What is the main drawback of a dual-slop ADC?
10.
Determine the values of LSB and MSB for an 8-bit DAC for 0V to 10V range. (K2)
11.
Define quantization error.
12.
What are advantages and disadvantages of R-2R ladder DAC?
13.
Name the essentials parts of a DAC.
14.
what is settling time?
15. Define accuracy of converter

16.
What is meant by linearity?
17. Find the resolution of an 8-bit DAC.

18.
What is a sample and hold circuit? Where it is used?
19.
Illustrate the working of sample and hold circuit with its circuit diagram and output waveform
20.
Define sample and hold period.
PART C
Q. Part A
No. (Multiple Choice Questions)
PART B
1. Define multivibrator?

2. Design an adjustable LM317 based voltage regulator for a output voltage of 5V with
Vref=1.25V, Iadj=100µA and R1=240Ω
3. Outline the pin diagram of LM317 voltage regulator

4. Mention the drawbacks of linear regulators:

5. Write the frequency of oscillation equation for triangular wave generator

6. Define 555 timer IC and infer how it is useful in electronic applications (K2)

7. Draw the pin diagram of 555 timer IC (K1)

8.
Recall the functional block diagram of 555 timer IC with neat sketch(K1)
9.
Distinguish one shot multivibrator from free running multivibrator. (K2)
10.
List the applications of mono-stable multivibrator. (K1)
11.
Summarize the applications of 555 timer in monostable mode of operation. (K1)
12.
List the applications of 555 timer in Astable mode of operation(K1)
13. In a astable multivibrator using 555 timer Ra=6.8K, Rb = 3.3K, C=0.1uF. Determine the free
running frequency(K2)
14.
Write the expression for total time period of 555 timer in astable mode?
15. What is the use of reset pin of 555 timer?

16.
Define voltage regulators and give the types
17. What do you mean by linear voltage regulators?
 18.
What are the advantages of adjustable voltage regulators over the fixed voltage regulators?
19.
What are the three different wave forms generated by ICL8038?
20.
Mention two applications of frequency to voltage converter.
Here are concise and informative answers to your questions related to multivibrators, 555 timers,
LM317, and voltage regulators:

1. Define Multivibrator:

A multivibrator is an electronic circuit used to implement a variety of simple two-state systems such
as oscillators, timers, and flip-flops.

2. Design an LM317 for 5V Output:

LM317 Output Voltage Equation:

Vout=Vref(1+R2R1)+Iadj⋅R2V_{\text{out}} = V_{\text{ref}} \left(1 + \frac{R_2}{R_1} \right) + I_{\

text{adj}} \cdot R_2

Given:

 Vref=1.25 VV_{\text{ref}} = 1.25\,V

 Iadj=100 μAI_{\text{adj}} = 100\,\mu A

 R1=240 ΩR_1 = 240\,\Omega

 Vout=5 VV_{\text{out}} = 5\,V

Solve for R2R_2:

5=1.25(1+R2240)+100×10−6⋅R25 = 1.25 \left(1 + \frac{R_2}{240} \right) + 100 \times 10^{-6} \cdot

R_2 3.75=1.25⋅R2240+0.0001R23.75 = \frac{1.25 \cdot R_2}{240} + 0.0001 R_2
3.75=R2(1.25240+0.0001)⇒R2=3.750.00531≈706.2 Ω3.75 = R_2 \left( \frac{1.25}{240} + 0.0001 \
right) \Rightarrow R_2 = \frac{3.75}{0.00531} \approx \boxed{706.2\,\Omega}

Choose R₂ ≈ 710 Ω (standard value).

3. Pin Diagram of LM317:

 Pin 1: Adjust

 Pin 2: Output

 Pin 3: Input

4. Drawbacks of Linear Regulators:

 Low efficiency (especially with large input-output difference)

 Heat generation (requires heat sinks)

 Bulky in high-power applications

  Not suitable for step-up voltage applications

5. Frequency of Oscillation – Triangular Wave Generator:

f=12⋅R⋅Cf = \frac{1}{2 \cdot R \cdot C}

Where R and C are timing resistor and capacitor.

6. Define 555 Timer IC:

A 555 timer IC is a highly stable IC used for generating accurate time delays or oscillations in
monostable and astable modes.

Use in electronics:

 Pulse generation

 Time delay circuits

 Oscillators

 Frequency generation

7. Pin Diagram of 555 Timer IC:

 Pin 1: GND

 Pin 2: Trigger

 Pin 3: Output

 Pin 4: Reset

 Pin 5: Control Voltage

 Pin 6: Threshold

 Pin 7: Discharge

 Pin 8: VCC

8. Functional Block Diagram of 555 Timer IC:

Includes:

 Two comparators

 SR flip-flop

 Discharge transistor

 Output stage

 Voltage divider (3 equal resistors)

(Schematic can be drawn upon request)

9. One-Shot vs Free-Running Multivibrator:

Feature Monostable (One-Shot) Astable (Free-Running)

Trigger Requires external trigger No trigger needed

Output One pulse per trigger Continuous square wave

Applications Timers, delay generators Oscillators, clocks

10. Applications of Monostable Multivibrator:

 Timers

 Pulse stretchers

 Missing pulse detectors

 Debouncing switches

11. Applications of 555 Timer in Monostable Mode:

 Timer circuits

 Pulse width modulation

 Frequency counters

 Digital delay timers

12. Applications of 555 Timer in Astable Mode:

 LED flashers

 Tone generators

 Pulse trains

 Square wave oscillators

13. Astable Frequency with Given Values:

f=1.44(Ra+2Rb)⋅C=1.44(6.8k+2⋅3.3k)⋅0.1μF=1.44(13.4k)⋅0.1μF≈1.07 kHzf = \frac{1.44}{(R_a + 2R_b) \

cdot C} = \frac{1.44}{(6.8k + 2 \cdot 3.3k) \cdot 0.1\mu F} = \frac{1.44}{(13.4k) \cdot 0.1\mu F} \
approx \boxed{1.07\,kHz}

14. Time Period of 555 Timer in Astable Mode:

T=0.693⋅(Ra+2Rb)⋅CT = 0.693 \cdot (R_a + 2R_b) \cdot C

15. Use of Reset Pin (Pin 4) in 555 Timer:

 Used to reset the timer output to LOW anytime

  Active LOW input (connect to Vcc if not used)

16. Define Voltage Regulators and Types:

Voltage Regulator: A circuit that maintains a constant output voltage regardless of input voltage or
load changes.

Types:

 Linear regulators (e.g., 78XX, LM317)

 Switching regulators (Buck, Boost, Buck-Boost)

 Zener diode-based regulators

17. What Are Linear Voltage Regulators?

 Regulate voltage by dissipating excess energy as heat

 Simple and low-noise but inefficient for large voltage drops

18. Advantages of Adjustable Voltage Regulators:

 Variable output voltage

 Fewer variants needed

 Better for custom designs

 Can achieve higher precision

19. Waveforms Generated by ICL8038:

 Sine wave

 Square wave

 Triangular wave

20. Applications of Frequency to Voltage Converter:

 Tachometers (RPM measurement)

 Frequency counters

 Digital-to-analog conversion for signal processing

Would you like labeled diagrams for the 555 timer internal blocks or the waveforms of ICL8038?