Operational Amplifiers

Transcription

1 Questions Easy Operational Amplifiers 1. Which of the following statements are true? a. An op-amp has two inputs and three outputs b. An op-amp has one input and two outputs c. An op-amp has two inputs and one output d. An op-amp has one input and one output 2. The output voltage of op-amp is a. Proportional to the difference between the two input voltages b. Proportional to the sum of the two input voltages c. Proportional to the product of the two input voltages 3. Negative feedback in an op-amp a. Increases the voltage gain b. Decreases the voltage gain c. Can change it to an oscillator 4. Which of the following statements are true?

2 a. The compensating capacitor increases the bandwidth of the circuit b. The compensating capacitor limits the bandwidth of the circuit c. The compensating capacitor does not change the bandwidth of the circuit 5. Which of the following statements are true? a. The compensating capacitor increases the speed of the op-amp b. The compensating capacitor increases the stability of the op-amp c. The compensating capacitor decreases the stability of the op-amp 6. Which of the following statements are true? a. The output stage is an unity gain stage b. The output stage provides the current-gain to drive the load c. Both of the above 7. The gain of an op-amp is given as a. b.

3 c. 8. Gain bandwidth product of an amplifier after inclusion of negative feedback a. Decreases b. Increases c. Remains same d. Either of a and b 9. Another name for a unity gain amplifier is a. Difference amplifier b. Comparator c. Single ended amplifier d. Voltage follower 10. Which of the following statements are true? a. The compensation capacitor is present in the third stage of the op-amp b. The compensation capacitor is present in the second stage of the op-amp c. The compensation capacitor is present in the first stage of the opamp d. The compensation capacitor is present in all the stages

4 Medium(Multiple options correct) 11. Which of the following statements about op-amp are true? a. Bandwidth increases as the gain increases. b. Bandwidth decreases as the gain increases. c. Bandwidth remains same as gain changes. d. Can't say anything 12. Which of the following statements are true? a. At the cutoff frequency, the voltage-gain becomes half of that in the pass-band. b. At the cutoff frequency, the current-gain becomes half of that in the pass-band. c. At the cutoff frequency, the power-gain becomes half of that in the pass-band. d. All of the above 13. Which of the following statements about op-amp are true? a. The gain-bandwidth product increases as the op-amp gain increases. b. The gain-bandwidth product decreases as the op-amp gain increases. c. The gain-bandwidth product remains same as the op-amp bandwidth changes.

5 d. The gain-bandwidth product remains same as the op-amp gain increases. 14. Unity-gain frequency is a. The frequency at which the gain becomes equal to unity b. Greater than the cutoff frequency c. Smaller than the cutoff frequency d. Equal to the gain-bandwidth product 15. In the gain expression a. The cutoff frequency is b. The cutoff frequency is c. The cutoff frequency is d. The cutoff frequency is 16. In the gain expression a. The unity-gain frequency is b. The unity-gain frequency is c. The unity-gain frequency is d. The unity-gain frequency is

6 17. Which of the following statements are true? a. The op-amp slew rate is the maximum rate of change of the output-voltage b. The op-amp slew rate is the maximum rate of change of the inputvoltage c. The op-amp slew rate is a measure of how fast the output voltage can change with the input voltage 18. Which of the following statements are true? a. Slew rate increases as the compensation capacitance increases b. Slew rate decreases as the compensation capacitance increases c. Slew rate remains same as the compensation capacitance increases d. Can't say anything 19. Which of the following statements are true? a. Op-amp slew rate increases as the input-state diff-amp tail current increases b. Op-amp slew rate decreases as the input-state diff-amp tail current increases c. Op-amp slew rate remains same as the input-state diff-amp tail current increases

7 d. Can't say anything 20. Which of the following statements are true? a. Compensation capacitor is also known as Bypass capacitor b. Compensation capacitor is also known as Coupling capacitor c. Compensation capacitor is also known as Miller capacitor Hard(Multiple options correct) 21. For a step-function input of voltage V, given to an op-amp with slew rate SR, then the maximum rate of change of output voltage is a. V times unity gain frequency b. SR c. Larger one between a and b d. Smaller one between a and b 22. A sine wave is given as input to an op-amp. Which of the following statements are true? a. When the op-amp is not slewing, the output voltage is a sine wave b. When the op-amp is driven into full-slewing, the output voltage is a sine wave c. When the op-amp is driven into full-slewing, the output voltage is a triangular wave d. When the op-amp is driven into full-slewing, the output voltage is a square wave

8 23. A sine wave is given as input to an op-amp. The op-amp is driven into full-slewing, then which of the following statements are true? a. The maximum output voltage increases as the amplitude of the sine wave increases b. The maximum output voltage does not depend on the amplitude of the sine wave c. The maximum output voltage does not depend on the frequency of the sine wave d. The maximum output voltage increases as the frequency of the sine wave decreases 24. A sine wave is given as input to an op-amp. Which of the following statements are true? a. As the frequency of the sine wave increases, the op-amp will eventually go into slewing b. As the frequency of the sine wave increases and the op-amp is not slewing, the maximum output voltage decreases. c. As the frequency of the sine wave increases and the op-amp is in slewing, the maximum output voltage decreases. d. All of the above 25. Which of the following statements about full-power bandwidth (FPBW) frequency are true? a. FPBW frequency is the 3-dB frequency

9 b. FPBW frequency is the highest frequency at which the op-amp can drive a sine wave of particular amplitude without going into slewing c. FPBW frequency is directly proportional to the amplitude of the sine wave d. FPBW frequency is inversely proportional to the amplitude of the sine wave 26. A 741-type OP-AMP has a gain-bandwidth product of 1MHz. A noninverting amplifier using this opamp& having a voltage gain of 20db will exhibit -3db bandwidth of a. 50 khz b. 1 MHz c. 100 khz d. 1000/17 khz 27. Which of the following statements are true? a. The second stage of an op-amp is a unity-gain stage b. The second stage of an op-amp is a high-gain stage c. The second stage of an op-amp is a non-inverting-gain stage d. The second stage of an op-amp is an inverting-gain stage 28. An OP-AMP has a slew rate of 5 V/µS. The largest sine wave input voltage possible at a frequency of 1 MHZ is a. 10 V b. 5 V c. 5/2 V d. 5/2 V

10 29. For a step-function input of voltage V, given to an op-amp with slew rate SR, then the maximum rate of change of output voltage is a. Directly proportional to V b. Inversely proportional to V c. Directly proportional to the Gain-Bandwidth product d. Inversely proportional to the Gain-Bandwidth product 30. An amplifier is using an op-amp with slew rate SR = 1v/µs and has a gain of 40db. If this amplifier has to faithfully amplify sinusoidal signals from dc to 200 KHz without introducing any slew-rate induced distortion, then the input signal level must not exceed a mv b. 796 mv c mv d. 395 mv Answers: 1. c 2. a 3. b 4. b 5. b 6. c 7. a 8. c 9. d 10. b

11 11. b 12. c 13. c,d 14. a,b,d 15. d 16. c 17. a,c 18. b 19. a 20. c 21. d 22. a,c 23. b,d 24. a,c 25. b,d 26. c 27. b,d 28. d 29. a,c 30. b