Free Electronics and Devices MCQs with Answers

• A. c. power into a.c. power
• B. c. power into d.c. power
• C. high resistance into low resistance
• D. none of the above

Explanation: A transistor uses DC supply power to produce a controlled AC output signal, so it is commonly described as converting DC power into AC…

• A. Electrolytic
• B. Mica
• C. Paper
• D. Air

Explanation: Electrolytic capacitors are commonly used for coupling and emitter bypassing because they provide large capacitance in a small, economical…

• A. The same as
• B. Less than
• C. More than
• D. None of the above

Explanation: A transistor's intrinsic collector output resistance is usually high, while the external collector load RC is selected at a lower value to…

• A. Transistor
• B. Biasing circuit
• C. Collector supply VCC
• D. None of the above

Explanation: The transistor does not create energy; it controls the larger power drawn from the collector supply VCC and transfers it to the load.

• A. Emitter is heavily doped
• B. Collector has reverse bias
• C. Collector is wider than emitter or base
• D. None of the above

Explanation: The reverse-biased collector-base junction gives the transistor a high resistance at its output, producing high output impedance in…

• A. The same as
• B. Less than
• C. More than
• D. None of the above

Explanation: The d.c. load normally includes the collector and emitter resistances in series, whereas the a.c.

• A. Transistor will be destroyed
• B. Biasing conditions will change
• C. Signal will not reach the base
• D. None of the above

Explanation: The input coupling capacitor normally blocks d.c. while passing the signal; shorting it allows the source's d.c.

• A. Grounded emitter
• B. Grounded base
• C. Grounded collector
• D. None of the above

Explanation: In a common-emitter amplifier, the emitter terminal is common to both the input and output circuits, usually being connected to ground…

• A. High
• B. Very high
• C. Moderate
• D. Low

Explanation: A low-resistance load heavily loads the amplifier, reducing the output voltage for a given input signal.

• A. 1000
• B. A million
• C. 100
• D. 10000

Explanation: The antenna signal may be only microvolts, while the speaker requires a signal of roughly volts, so several amplification stages may…

• A. Increase the output impedance of transistor
• B. Protect the transistor
• C. Pass a.c. and block d.c.
• D. Provide biasing

Explanation: A coupling capacitor transfers the varying a.c. signal from one amplifier stage to the next while preventing the d.c.

• A. 10 db
• B. 20 db
• C. 40 db
• D. None of the above

Explanation: Power gain in decibels is 10 log₁₀(Pout/Pin), so 10 log₁₀(100) = 20 dB. Using 20 log for a power ratio would incorrectly give 40 dB.

• A. Thin base
• B. Thin collector
• C. Wide emitter
• D. None of the above

Explanation: A thin base allows more carriers injected from the emitter to reach the collector, increasing transistor action and voltage gain.

• A. Short
• B. Open
• C. Partially short
• D. None of the above

Explanation: For the d.c. equivalent circuit, capacitors block steady-state current after charging, so they are replaced by open circuits.

• A. Avoid voltage gain drop
• B. Forward bias the emitter
• C. Reduce noise in the amplifier
• D. None of the above

Explanation: The emitter capacitor bypasses the a.c. signal around RE, reducing emitter degeneration and preventing the voltage gain from falling.

• A. Reverse bias the emitter
• B. Forward bias the collector
• C. Set up operating point
• D. None of the above

Explanation: D.C. bias conditions establish the transistor's quiescent operating point, usually selected in the active region for faithful…

• A. Short
• B. Open
• C. Partially open
• D. None of the above

Explanation: At signal frequencies in the a.c. equivalent circuit, coupling and bypass capacitors are assumed to have negligible reactance, so they act…

• A. RL + RC
• B. RC || RL
• C. RL - RC
• D. RC

Explanation: The collector resistor and load are both connected from the collector's a.c. node to ground, so the a.c.

• A. Protect the transistor
• B. Cool the transistor
• C. Couple or bypass a.c. component
• D. Provide biasing

Explanation: Amplifier capacitors commonly couple the a.c. signal between stages or bypass a resistor for a.c. signals while blocking d.c.

• A. α
• B. (1 + α)
• C. (1+ β)
• D. β

Explanation: For a CE amplifier, the voltage gain can be written approximately as Av = β(RAC/Rin), where β is the common-emitter current gain.