Electronics Devices & Circuits

Op-Amp Characteristics Viva Questions

Op-Amp Characteristics Viva Questions

Op-Amp Characteristics Viva Questions, Operational Amplifier Characteristics Viva Questions, Viva Questions on Op-Amp, Engineering Viva Questions, Electronics Device Circuits Viva Questions

Short Questions with Answers

Q.1. Define input Bias.

Ans. It is defined as the average of the two DC currents at the inputs of an op-amp.

Q.2. Define Input Impedance.

Ans. It is defined as the impedance seen by a signal source at the input terminals of an amplifier.

Q.3. Define input offset current.

Ans. It is defined as the difference between the two op-amp input currents.

Q.4. Define Input Offset Voltage.

Ans. It is defined as the magnitude of DC voltage which, if applied to input terminals, would reduce op-amp output DC voltage to zero.

Q.5. What is an operational amplifier? Explain.

Ans. It is a high-gain integrated-circuit, direct coupled amplifier with differential input terminals.

Q.6. Define Output Impedance.

Ans. It is the impedance seen looking back at the output terminals of an amplifier, i.e., the thevenin equivalent impedance seen at the output.

Q.7. What are Saturation Voltages?

Ans. The maximum and minimum voltage levels at which the output of an op-amp can assume based upon given power supply voltage.

Q.8. What is Slew Rate?

Ans. It is the maximum rate at which the output of an op-amp can change. It is usually expressed in volts/ microsecond.

Q.9. What do you mean by Slew Rate Limiting Frequency?

Ans. It is the highest frequency that can be processed in a circuit without distortion as a result of the slew rate.

Q.10. What is a DIP?

Ans. It is an acronym for dual-in-line package, a package configuration having equal number of pins spaced 0.1 inch apart in two parallel rows.

Q.11. What is meant by open-loop mode?

Ans. It represents the situation in which an operational amplifier is operated without external feedback.

Q.12. Define open-loop gain.

Ans. It is the voltage gain of the operational amplifier without any external feedback.

Q.13. What is meant by Gain Bandwidth Product?

Ans. It is a specification for an op-amp giving product of the DC gain and the 3-dB bandwidth. It is equal o the unity-gain frequency.

Q.14. What is current gain?

Ans. It is the ratio of output current to input current.

Q.15. What is voltage gain?

Ans. It is the ratio of output voltage to input voltage.

Q.16. What do you mean by operating temperature?

Ans. It is the ambient temperature for which the operational amplifier operates within the manufacturer’s specifications.

Q.17. Define output voltage swing.

Ans. It is defined as the maximum peak output voltage which the operational amplifier can produce without saturation or clipping. It is typically about two diode voltage drops less than the corresponding supply voltages.

Q.18. Define power-supply rejection ratio (PSRR).

Ans. It is defined as the ratio of the change in input offset voltage of an operational amplifier to a corresponding change in the supply voltage. It is also known as the power-supply sensitivity.

Q.19. What is meant by unity-gain frequency?

Ans. It is the frequency at which the operational amplifier’s open-loop gain is unity. It is also known as either the unity-gain crossover frequency or the small-signal unity-gain bandwidth.

Q.20. Mention the various stages in an op-amp.

Ans. The various stages in an op-amp are as under:

  • Input stage
  • Intermediate stage
  • Level translator (or) Buffer stage
  • Output stage

Q.21. What is the gain of an ideal op-amp?

Ans. The gain of an ideal op-amp is infinity.

Q.22. If the output voltage simultaneously changes with the input then what is the value of slew rate?

Ans. The value tends to infinity.

Q.23. Define common mode rejection ratio (CMRR) and give an expression.

Ans. The relative sensitivity of an op-amp to a difference signal as compounded to a common mode signal is called as common mode rejection ratio (CMRR). It is the ratio of differential gain (Aid) to the common mode gain (Acm).

CMRR=\frac{A_{id}}{A_{cm}}

It is usually expressed in decibels (dB). Higher is the value of CMRR, better is the op-amp.

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