Current Mirrors MCQs

Practice Current Mirrors MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1

Analog ElectronicsCurrent Mirrors

A basic two-transistor BJT current mirror is designed primarily to?

AGenerate an approximately replicated current
BGenerate a sine wave
CProvide voltage gain of exactly 100
DConvert AC directly to RF

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Correct Answer: A. Generate an approximately replicated current

Explanation: Matched transistors with equal base-emitter voltages can be arranged so an output collector current approximately mirrors a reference current.

Reference: Standard analog electronics: current mirrors

Question 2

Analog ElectronicsCurrent Mirrors

In a simple matched BJT current mirror, neglecting base currents and Early effect, if the reference current is 1 mA, the mirrored output current is approximately?

A0.1 mA
B0.5 mA
C1 mA
D10 mA

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Correct Answer: C. 1 mA

Explanation: Under ideal matched-device assumptions, the output current approximately equals the reference current.

Reference: Standard analog electronics: current mirrors

Question 3

Electronic Devices & CircuitsCurrent Mirrors

A current mirror is commonly used in integrated analog circuits primarily to?

AReplicate or establish bias currents
BGenerate optical isolation
CPerform rectification only
DStore digital data permanently

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Correct Answer: A. Replicate or establish bias currents

Explanation: Matched transistors arranged as a current mirror provide approximately replicated reference currents and are widely used for IC biasing and active loads.

Reference: Standard analog electronics: current mirror

Question 4

Electronic Devices & CircuitsCurrent Mirrors

In an ideal BJT current mirror using matched transistors, the reference current is 2 mA. Neglecting base currents and mismatch, the mirrored output current is approximately?

A0.2 mA
B1 mA
C2 mA
D20 mA

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Correct Answer: C. 2 mA

Explanation: For matched transistors with equal base-emitter voltage, the ideal mirror reproduces the reference current, so the output is approximately 2 mA.

Reference: Standard analog electronics: ideal BJT current mirror

Question 5

Electronic Devices & CircuitsCurrent Mirrors

The principal advantage of a Widlar current source over a simple current mirror is its ability to generate?

AA relatively small output current without requiring an extremely large resistor
BAn AC voltage with zero DC bias
CInfinite current gain
DA digital clock signal

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Correct Answer: A. A relatively small output current without requiring an extremely large resistor

Explanation: Emitter degeneration in one mirror transistor allows the Widlar circuit to produce small bias currents using practical resistor values.

Reference: Standard analog electronics: Widlar current source

Question 6

Electronic Devices & CircuitsCurrent Mirrors

Compared with a simple current mirror, a cascode current mirror is mainly used to obtain?

AHigher output resistance and better current-source behavior
BLower input resistance only
CZero supply voltage
DA square-wave output

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Correct Answer: A. Higher output resistance and better current-source behavior

Explanation: The cascode arrangement reduces the effect of output-voltage variation on mirrored current, substantially increasing output resistance.

Reference: Standard analog electronics: cascode current mirror

Question 7

Analog ElectronicsCurrent Mirrors

A Wilson current mirror is commonly preferred over a simple two-transistor mirror because it offers?

AImproved current accuracy and higher output resistance
BZero transistor count
CNo need for a reference current
DOnly AC operation

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Correct Answer: A. Improved current accuracy and higher output resistance

Explanation: The Wilson topology uses feedback to reduce base-current-related error and generally raises output resistance compared with a simple mirror.

Reference: Standard analog electronics: Wilson current mirror

Question 8

Analog ElectronicsCurrent Mirrors

A Widlar current source is especially useful in integrated circuits for generating?

ASmall currents using practical resistor values
BVery large RF power directly
COnly alternating current
DA precisely zero output current

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Correct Answer: A. Small currents using practical resistor values

Explanation: Emitter degeneration in the Widlar arrangement allows currents much smaller than the reference current without requiring impractically large on-chip resistors.

Reference: Standard analog electronics: Widlar current source

Question 9

Analog ElectronicsCurrent Mirrors

In a basic BJT current mirror, finite transistor beta causes the output current to differ from the ideal reference mainly because?

AThe reference branch must also supply base currents
BCollector resistors become inductors
CThe Early voltage becomes zero
DBoth transistors enter breakdown automatically

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Correct Answer: A. The reference branch must also supply base currents

Explanation: The reference current supplies the diode-connected transistor collector current plus the base currents of the mirror transistors, producing finite-beta error.

Reference: Standard analog electronics: current-mirror error