Ideal Operational Amplifier MCQ [Free PDF] - Objective Question Answer for Ideal Operational Amplifier Quiz

1. Determine the output from the following circuit

A. 180^o in phase with an input signal
B. 180^o out of phase with an input signal
C. Same as that of an input signal
D. Output signal cannot be determined

Answer: B

The input signal is given to the inverting input terminal. Therefore, the output V_o is 180^o out of phase with input signal V₂.

2. Which of the following electrical characteristics is not exhibited by an ideal op-amp?

A. Infinite voltage gain
B. Infinite bandwidth
C. Infinite output resistance
D. Infinite slew rate

Answer: C

An ideal op-amp exhibits zero output resistance so that output can drive an infinite number of other devices.

3. An ideal op-amp requires infinite bandwidth because

A. Signals can be amplified without attenuation
B. Output common-mode noise voltage is zero
C. Output voltage occurs simultaneously with input voltage changes
D. Output can drive the infinite number of device

Answer: A

An ideal op-amp has infinite bandwidth. Therefore, any frequency signal from 0 to ∞ Hz can be amplified without attenuation.

4. Ideal op-amp has infinite voltage gain because

A. To control the output voltage
B. To obtain a finite output voltage
C. To receive zero noise output voltage
D. None of the mentioned

Answer: B

As the voltage gain is infinite, the voltage between the inverting and non-inverting terminal (i.e. differential input voltage) is essentially zero for finite output voltage.

6. Find the output voltage of an ideal op-amp. If V₁ and V₂ are the two input voltages

A. V_O= V₁-V₂
B. V_O= A×(V₁-V₂)
C. V_O= A×(V₁+V₂)
D. V_O= V₁×V₂

Answer: B

The output voltage of an ideal op-amp is the product of gain and the algebraic difference between the two input voltages.

7. How will be the output voltage obtained for an ideal op-amp?

A. Amplifies the difference between the two input voltages
B. Amplifies individual voltages input voltages
C. Amplifies products of two input voltage
D. None of the mentioned

Answer: A

Op-amp amplifies the difference between two input voltages and the polarity of the output voltage depends on the polarity of the difference voltage.

8. Which is not the ideal characteristic of an op-amp?

A. Input Resistance –> 0
B. Output impedance –> 0
C. Bandwidth –> ∞
D. Open loop voltage gain –> ∞

Answer: A
Input resistance is infinite so almost any signal source can drive it and there is no loading of the preceding stage.

9. Find the input voltage of an ideal op-amp. It’s one of the inputs and output voltages are 2v and 12v. (Gain=3)

A. 8v
B. 4v
C. -4v
D. -2v

Answer: D

The output voltage, V_O = (Vin₁– Vin₂)

=> 12v = 3×(2- Vin₂)

=> Vin₂= -2v.

10. Which factor determine the output voltage of an op-amp?

A. Positive saturation
B. Negative saturation
C. Both positive and negative saturation voltage
D. Supply voltage

Answer: C

The output voltage is proportional to the input voltage only until it reaches the saturation voltage. The output cannot exceed the positive and negative saturation voltage. These saturation voltages are specified by an output voltage swing rating of the op-amp for given values of the supply voltage.

11. Open-loop op-amp configuration has

A. Direct network between output and input terminals
B. No connection between output and feedback network
C. No connection between input and feedback network
D. All of the mentioned

Answer: A

In an open-loop configuration, the output signal is not fed back in any form as part of the input signal and the loop that would have been formed with feedback is open.

12. In which configuration does the op-amp function as a high gain amplifier?

A. Differential amplifier
B. Inverting amplifier
C. Non-inverting amplifier
D. All of the mentioned

Answer: D

An op-amp function as a high gain amplifier when connected in an open-loop configuration. These three are the open-loop configuration of an op-amp.

13. How does the open-loop op-amp configuration classified?

A. Based on the output obtained
B. Based on the input applied
C. Based on the amplification
D. Based on the feedback network

Answer: B

Open-loop configurations are classified according to the number of inputs used and the terminal to which the input is applied when a single input is used.

14. What will be the voltage drop across the source resistance of the differential amplifier when connected in an open-loop configuration?

A. Zero
B. Infinity
C. One
D. Greater than one

Answer: A

The source resistances are normally negligible compared to the input resistance. Therefore, the voltage drop across input resistors can be assumed to be zero.

15. The output voltage of an open-loop differential amplifier is equal to

A. Double the difference between the two input voltages
B. Product of voltage gain and individual input voltages
C. Product of voltage gain and the difference between the two input voltages
D. Double the voltage gain and the difference between two input voltages

Answer: C

The output voltage is equal to the product of voltage gain and the difference between the two input voltages.

16. Calculate the output voltage for the given circuit.

A. V_o = 7v
B. V_o = 5.9v
C. V_o = 12v
D. V_o = 11.4v

Answer: C

The output voltage, V_o = A*(V_in1-V_in2).(Since R_in1 and R_in2 are negligible compared to input resistance in an open-loop differential amplifier).

=> V_o = 4*(12v-9v) = 12v.

17. Find the output of inverting amplifier?

A. V_o = AV_in
B. V_o = -AV_in
C. V_o = -A(V_in1– V_in2)
D. None of the mentioned

Answer: B

In an inverting amplifier, the input signal is amplified by gain A and is also inverted at the output. The negative sign indicates that the output voltage is of opposite polarity.

18. Determine the output voltage for the non-inverting amplifier input voltage 37µVpp sinewave. Assume that the output is a 741.

A. -7.44 Vpp sinewave
B. 74 Vpp sinewave
C. 7.4Vpp sinewave
D. 0.7 Vpp sinewave

Answer: C

The output voltage for non-inverting amplifier V_o = A*V_in = 200000 * 37µ = 7.4 Vpp sinewave.

19. What happens if any positive input signal is applied to an open-loop configuration?

A. Output reaches saturation level
B. Output voltage swing’s peak to peak
C. Output will be a sine waveform
D. Output will be a non-sinusoidal waveform

Answer: A

In open-loop configuration, due to the very high gain of the op-amp, any input signal slightly greater than zero drives the output to saturation level.

20. Why open-loop op-amp configurations are not used in linear applications?

A. Output reaches positive saturation
B. Output reaches negative saturation
C. Output switches between positive and negative saturation
D. Output reaches both positive and negative saturation

Answer: C

When operated in an open loop, the output switches between positive and negative saturation levels. For this reason, open-loop op-amp configurations are not used in linear applications.

21. A feedback amplifier is also called as

A. Open-loop amplifier
B. Closed-loop amplifier
C. Feedback network amplifier
D. Looped network amplifier

Answer: B

A feedback amplifier is sometimes referred to as a closed-loop amplifier because the feedback forms a closed loop between input and output.

22. How many types of configurations are available for feedback amplifiers?

A. Six
B. Four
C. Two
D. Eight

Answer: B

There are four types of configuration available. They are voltage series feedback, voltage shunt feedback, Current series feedback, and Current shunt feedback.

23. Which of the following is not a feedback configuration?

A. Current-series feedback
B. Voltage-shunt feedback
C. Current-Voltage feedback
C. Current-Shunt feedback

Answer: C

In a feedback amplifier, either current or voltage can be fed back to the input, but both current and voltage cannot be feedback simultaneously.

24. When load current flows into the feedback circuit, the configuration is said to be

A. Current-shunt feedback
B. Voltage-shunt feedback
C. Voltage-series feedback
D. All of the mentioned

Answer: B

In the current-series and current-shunt feedback circuit, the load current flows into the feedback circuit.

25. On what criteria does the feedback amplifier are classified?

A. Signal fed back to the input
B. Signal applied to an input
C. Signal fed back to an output
D. None of the mentioned

Answer: D

The feedback amplifiers are classified according to whether the voltage or current is fed back to the input in series or parallel.

26. The closed-loop voltage gain is reciprocal of

A. Voltage gain of an op-amp
B. Gain of the feedback circuit
C. Open loop voltage gain
D. None of the mentioned

Answer: B

Comparing the equation of closed loop voltage gain (A_F) and the gain of the feedback circuit (B.. A_F is reciprocal of B

=> A_F = 1+( R_F/ R₁) ; B= R₁/( R₁+ R_F)

=> B = 1+( R₁/ R_F)

Therefore, A_F = 1/B.

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