Transistors Questions with Answers

Transistors are semiconductor devices that amplify and switch electronic signals, forming the foundation of most circuits. They are a frequent topic in aptitude questions and answers for GATE, ISRO, and core electronics placement exams. Understanding NPN and PNP transistor configurations, biasing, and current amplification helps analyze circuit behavior effectively. By practicing transistor aptitude questions with solutions PDF, aspirants can improve their conceptual clarity and application skills, which are crucial for clearing electronics-based technical exams and interviews.

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What is the most common application of a bipolar junction transistor (BJT)?

A Amplification
B Rectification
C Oscillation
D Modulation

Answer: Option A

Explanation: BJTs are widely used as amplifiers in electronic circuits to increase the strength of weak signals.

In a common emitter configuration, the input signal is applied between:

A Base and emitter
B Base and collector
C Emitter and collector
D Collector and ground

Answer: Option A

Explanation: In common emitter configuration, the base is the input terminal, emitter is common, and collector is the output.

What is the typical value of current gain (β) for a small signal transistor?

A 20-50
B 50-300
C 300-500
D 500-1000

Answer: Option B

Explanation: The current gain β for small signal transistors typically ranges from 50 to 300, with 100 being a common value.

Which transistor configuration provides both voltage and current gain?

A Common base
B Common emitter
C Common collector
D All configurations

Answer: Option B

Explanation: Common emitter configuration provides both voltage gain and current gain, making it the most widely used configuration.

What is the main advantage of FET over BJT?

A High input impedance
B High current gain
C Low noise
D Better linearity

Answer: Option A

Explanation: FETs have high input impedance due to their voltage-controlled operation, unlike current-controlled BJTs.

In a transistor, the region between base and collector is called:

A Base-emitter junction
B Base-collector junction
C Emitter-collector junction
D Depletion region

Answer: Option B

Explanation: The base-collector junction is typically reverse biased in normal amplifier operation.

What is the purpose of emitter bypass capacitor in CE amplifier?

A Increase voltage gain
B Reduce distortion
C Improve frequency response
D Provide DC bias

Answer: Option A

Explanation: The emitter bypass capacitor prevents AC negative feedback, thereby increasing the voltage gain.

Which transistor parameter indicates its high-frequency capability?

A Transition frequency (fT)
B Current gain (β)
C Early voltage
D Saturation voltage

Answer: Option A

Explanation: Transition frequency is the frequency where current gain drops to unity, indicating high-frequency performance.

What is the typical value of VBE for silicon transistor in active region?

A 0.2V
B 0.7V
C 1.2V
D 2.0V

Answer: Option B

Explanation: For silicon transistors, the base-emitter voltage is approximately 0.7V when forward biased in active region.

Q10

Which type of transistor is known as unipolar transistor?

A BJT
B JFET
C UJT
D Phototransistor

Answer: Option B

Explanation: FETs are unipolar because current conduction is due to only one type of charge carrier (electrons or holes).

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Transistors and Applications Questions and Answers

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