Linear Integrated circuits lab Viva Questions Part 1 ~ ECE School

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Viva Questions on Op Amps:

1.What are the advantages of integrated circuits?

· increased package density.

· Cost reduction .

· Increased system reliability.

· Improved functional performance.

· Increased operating speeds.

· Reduction in power consumption.

2.What are the popular IC packages available?

· Metal can package.

· Dualinlinepackage.

· Ceramic flat package.

3.What is an operational amplifier.

An operational amplifier is a directcoupled high gain amplifier consisting of one or more differential amplifiers, it can be used to perform a variety of mathematical operations.

4.What is the Internal Structure of op-amp and explain each block in brief?

5.What are the characteristics of an ideal op-amp.

· Open loop voltage gain is infinity.

· Input impedance is infinity.

· Output impedance is zero.

· Bandwidth is infinity.

· Zero offset.

· CMRR Infinite.

· Slew rate Infinite.

6.What are the DC,AC Characteristics of OP-Amp?

DC Characteristics: Input Bias Current, Input off set Current, Input offset voltage, Thermal Drift.

AC Characteristics: Slew Rate, Frequency compensation

7.What is input offset voltage?

It is the voltage Imbalance b/w two input terminals of op-amp.

8.Define input offset current.

The difference between the bias currents at the input terminals of the

9.Define CMRR of an opamp?

It is the ratio b/w Differential mode gain and common mode gain

CMRR= Ad/Ac

10.what is the effect of high frequency on its performance?

The openloopgain of op-ampdecreases at higher frequencies due to the presence of parasitic capacitance. The closedloopgain increases at higher frequencies and leads to instability.

11.What is the need for frequency compensation in practical op-amps?

When large bandwidth and lower closed loop gain is desired, to improve the stability.

12.What are the frequency compensation methods?

· Dominantpolecompensation

· Pole-zerocompensation

13.Define slew rate.

The maximum rate of change of output voltage causedby a step input voltage. An ideal slew rate is infinite. Units- v/µs

14.Can we use IC 741 for high frequency applications?

No, IC741 has a low slew rate.

15.Why slew rate is not infinite in Ideal op-amp?

There is a capacitor withinor outside of an op-ampto prevent oscillation.

16.What are the applications of op-amps?

Linear: Adder, subtracter, voltage to current converter, current to voltage converters, instrumentation amplifier, analog computation, power amplifier, Integrator, differentiator etc.

Non linear: Rectifier, peak detector, clipper, clamper, sample and hold circuit, log amplifier, anti-logamplifier, multiplier

17.What is an instrumentation amplifier and the need for?

In a number of industrial and consumer applications, the measurement of physical quantities is usually done with the help oftransducers. The output of transducer has to be amplified So that it can drive the indicator or display system. This function isperformed by an instrumentation amplifier.

18.What are the features of instrumentation amplifier?

· high gain accuracy

· high CMRR

· high gain stability

· low dc offset

· low output impedance

19.What are the applications of V-I and I-V converters?

V-I:Low voltage dc and ac voltmeter, L E D Tester, Zener diode tester

I-V: Digital to Analog converter, Light intensity indicator, photo diode detector

20.What do you mean by a precision diode?

The major limitation of ordinary diode is that it cannot rectify voltages below the cut in voltage of the diode the precision diode is capable of rectifying input signals of the orderof millivolt.

21.What are the applications of precision diode.

· Half waveRectifier

· Full Wave rectifier

· Peak value detector

· Clipper, Clamper

22.What are the applications of Log amplifier?

Multiplier, divider.

23.What are the limitations of the basic differentiator circuit?

At high frequency, a differentiator may become unstable and break into oscillations, The input impedance decreases with increase in frequency.

24.What are the limitations of the basic Integrator circuit?

At low frequency, a integrator may become unstable and break into oscillations, The input impedance decreases with decrees in frequency.

25. What is a comparator?

Which compares a signal with a known reference voltage . its output is either + Vsat or -Vsat .

26.What are the applications of comparator?

Zero crossing detector

27.Why can’t we use comparator to convert sin wave into square wave?

If noise exist in sinusoidal signal at zero volts unwantedly out put varies b/w + Vsat and -Vsat .

28.What is a Schmitt trigger?

It is a regenerative comparator. It converts sinusoidal input into a square wave output.

29.What is a multivibrator?

It is a regenerative circuit that is used extensively in timing applications. It has two states either stable or quasi-stable depending on the type of multivibrator.

30.What is monostable multivibrator?

Generates a single pulse of specified duration in response to each external trigger signal. It has only one stable state. Its is also called as One-shot generator.

31.What is an astable multivibrator?

It is a free running oscillator having two quasi-stable states. So it is a Square wave generator.

32.What is a bistable multivibrator?

Bistable multivibrator is one that maintains a given output voltage level unless an external trigger is applied .Application of an external trigger signal causes a change of state, and this output level is maintained indefinitely until an second trigger applied . Thus, it requires two external triggers before it returns to its initial state

33.What is the op Amp based Mono stable multivibrator out put signal pulse width?