QUESTIONS ON OP-AMPS

1. What is an op amp?

Ans: The term OP-AMP is used to denote an operational amplifier which can be configured to

          Perform various operations like amplification, subtraction, differentiation, addition, integration

           etc. Example is the very popular IC 741.

 2. Mention the characteristics of an ideal op amp

Ans: Infinite voltage gain, Infinite input impedance, Zero output impedance, Infinite bandwidth

        Zero input offset voltage (i.e., exactly zero out if zero in)

3. How the Op-amp used as a differential amplifier?

 Ans:    It is one of the Op-amp configurations, in which one input signal connected to Inverting

        terminal and another input signal connected to Non- Inverting terminal.

 4. Explain how an op amp can be used as an inverting amplifier

Ans:    An inverting amplifier is a special case of the differential amplifier in which that circuit's

         non-inverting input is grounded, and inverting input is connected to an input voltage.

5. Explain how an op amp can be used as an , non inverting amplifier

Ans:    An Non inverting amplifier is a special case of the differential amplifier in which that

       circuit's Inverting input is grounded, and Non-inverting input is connected to an input voltage.

 

6. Explain why open loop op amp configurations are not used in linear applications.

 Ans:     Op-amp is a high gain device .even a noise voltage can be amplified to large extent . if u r not

           using a feedback(normally negative) the out put of open loop configuration is always saturated

           we get only a constant saturated voltage

 7. Explain virtual ground concept.

Ans:    a virtual ground (or virtual earth) is a node of a circuit that is maintained at a steady reference

        potential, without being connected directly to the reference potential. In some cases the

        reference potential is considered to be that of the surface of the earth, and the reference node

         is called "ground" or "earth" as a consequence.

8. What is the gain of a buffer amplifier (Voltage follower)?

  

Ans: Unity

 9. Differentiate between open loop gain and closed loop gain.

  Ans:    Open loop gain is function of the output voltage and input voltage. Closed loop gain is

            function of   output voltage, input voltage and gain of feed back network.

10. Explain how an op amp can be used to add three signals.

 

 

 11. Define slew rate.

Ans:    The maximum rate of change of output voltage per unit of time and is expressed as V/ µ Sec.

12. Input bias current.

Ans:    The average of currents that flow into the non-inverting and inverting terminals of op-amp.

13 input offset voltage.

  Ans:    Differential DC voltage required between the inputs of an operational amplifier  to make

       the output zero.

 14. How can you use an op amp to integrate a signal?

Ans:    The Operational Amplifier circuit performs the mathematical operation of integration when

         input signal to the –amp is applied through resistor and feed back element is capacitor.

 

15. How op-amp can be used as differentiator?

Ans:    The Operational Amplifier circuit performs the mathematical operation of Differentiation

          when  input signal to the –amp is applied through capacitor and feed back element is resistor.

16.What is a Zero Crossing Detector?

 Ans: Zero cross detector detects the when the input signal crossing zero

         Eg: It converts sinusoidal signal to square wave signal.

 17. How can you use an op amp as a comparator ?

 Ans:    In open loop configuration Op-amp(operate in saturation region) used as a comparator.

18. what are the frequency compensation techniques?

Ans: External compensation,Internal compensation.

19. Give some Non-linear applications of an Op-Amp

Ans: Log amplifier, Precision rectifier…..ect

20. Give some linear applications of Op-Amp

Ans: Inverting amplifier, Non-inverting amplifier, Summing Amplifier, Integrator, Differentiator….ect

21. What is the Importance of Compensation Resistor at input terminal ?

    Compensation Resistor used to minimize the Input Bias current effect on output DC voltage.

22. What is Frequency respnce?

 Ans:    Frequency response is the manner in which the gain magnitude and the phase angle between

      the input and output respond to different frequencies.

23. What are the AC Characteristics of Op-Amp ?

Ans: Frequency response and Slew rate

24. What is the need of Compensation Networks?

Ans; Compensation Networks used to control the phase shift and thus improve the stability of

        Op- Amp.

25. What is Schmitt trigger?

Ans: A Schmitt trigger is a comparator with positive feedback that converts an irregular wave form to

        a square wave or pulse wave form