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Operational Amplifier

Study 30 Electrical Engineering MCQs with correct answers and explanations.

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21Electrical EngineeringMedium

For an Op-amp with negative feedback, the output is________?

Afed back to the noninverting input

Bfed back to the inverting input

Cincreased

Dequal to the input

Correct answer

B. fed back to the inverting input

Explanation

The correct answer is fed back to the inverting input.

22Electrical EngineeringMedium

A certain inverting amplifier has a closed-loop voltage gain of 25. The Op-amp has an open-loop voltage gain of 100,000. If an Op-amp with an open-loop voltage gain of 200,000 is substituted in the arrangement, the closed-loop gain________?

Aincreases slightly

Bremains at 25

Cdoubles

Ddrops to 12.5

Correct answer

B. remains at 25

Explanation

The correct answer is remains at 25.

23Electrical EngineeringMedium

The input stage of an Op-amp is usually a ________?

ACE amplifier

Bswamped amplifier

Cdifferential amplifier

Dclass B push-pull amplifier

Correct answer

C. differential amplifier

Explanation

The correct answer is differential amplifier.

24Electrical EngineeringMedium

Negative feedback________?

Adecreases the output impedance and bandwidth

Bincreases the input impedance and bandwidth

Cdoes not affect impedance or bandwidth

Dincreases the input and output impedances

Correct answer

B. increases the input impedance and bandwidth

Explanation

The correct answer is increases the input impedance and bandwidth.

25Electrical EngineeringMedium

The tail current in a differential amplifier equals ________?

Asum of two emitter currents

Bdifference between two emitter currents

Ccollector current divided by current gain

Dcollector voltage divided by collector resistance

Correct answer

A. sum of two emitter currents

Explanation

The correct answer is sum of two emitter currents.

26Electrical EngineeringMedium

In the common mode, ________?

Athe outputs are connected together

Ban identical signal appears on both the inputs

Cthe output signal are in-phase

Dboth inputs are grounded

Correct answer

B. an identical signal appears on both the inputs

Explanation

The correct answer is an identical signal appears on both the inputs.

27Electrical EngineeringMedium

The use of negative feedback ________?

Aanswers (A) and (B)

Bmakes the Op-amp oscillate

Cmakes linear operation possible

Dreduces the voltage gain of an Op-amp

Correct answer

A. answers (A) and (B)

Explanation

The correct answer is answers (A) and (B).

28Electrical EngineeringMedium

A differential amplifier________?

Ahas two outputs

Bhas one input and one output

Cis a part of an Op-amp

Danswers (A) and (B)

Correct answer

D. answers (A) and (B)

Explanation

The correct answer is answers (A) and (B).

29Electrical EngineeringMedium

The input offset current equals the________?

Anone of these

Baverage of two base currents

Ccollector current divided by current gain

Ddifference between two base currents

Correct answer

D. difference between two base currents

Explanation

The correct answer is difference between two base currents.

30Electrical EngineeringMedium

The common-mode voltage gain of a differential amplifier is equal to RC divided by ________?

A2RE

Br’e

C2r’e

Dr’e/2

Correct answer

A. 2RE

Explanation

The correct answer is 2RE.

Negative feedback________?

Adecreases the output impedance and bandwidth

Bincreases the input impedance and bandwidth

Cdoes not affect impedance or bandwidth

Dincreases the input and output impedances

Correct answer

B. increases the input impedance and bandwidth

Explanation

The correct answer is increases the input impedance and bandwidth.