Free Electronics and Devices MCQs with Answers
758 Electronics and Devices MCQs from Electrical Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
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758 questions · page 30 of 38
- A. Zero
- B. Low
- C. High
- D. None of the above
Explanation: The input is applied at the base, and the emitter follower's feedback action makes the input resistance high.
Correct answer: High- A. germanium
- B. silicon
- C. carbon
- D. none of the above
Explanation: Silicon is the most widely used transistor semiconductor because it is abundant, thermally stable, and has a smaller leakage current than…
Correct answer: silicon583. If voltage feedback (negative) is applied to an amplifier, its output impedance ______________?
- A. Remains the same
- B. Is increased
- C. Is decreased
- D. None of the above
Explanation: Voltage-series negative feedback lowers output impedance because the feedback amplifier opposes changes in output voltage.
Correct answer: Is decreased- A. Much less than 1
- B. Approximately equal to 1
- C. Greater than 1
- D. None of the above
Explanation: The emitter voltage follows the base voltage, differing mainly by the nearly constant base-emitter drop, so the voltage gain is slightly…
Correct answer: Approximately equal to 1- A. increase the forward current
- B. decrease the forward current
- C. compensate for excessive doping
- D. prevent excessive temperature rise
Explanation: A heat sink conducts heat away from the transistor and increases the area available for cooling.
Correct answer: prevent excessive temperature rise- A. high resistance to low resistance
- B. low resistance to high resistance
- C. high resistance to high resistance
- D. low resistance to low resistance
Explanation: A transistor transfers a signal from its relatively low-resistance input circuit to its high-resistance output circuit.
Correct answer: low resistance to high resistance- A. remain the same
- B. increase
- C. decrease
- D. none of the above
Explanation: For the same transistor junction bias voltages, the emitter, base, and collector currents are determined by those voltages and transistor…
Correct answer: remain the same588. When current feedback (negative) is applied to an amplifier, its output impedance ________________?
- A. Is increased
- B. Is decreased
- C. Remains the same
- D. None of the above
Explanation: Negative current feedback samples output current and opposes its variation, making the amplifier behave more like a current source.
Correct answer: Is increased- A. ICBO
- B. ICEO
- C. IC
- D. IE
Explanation: Using α = IC/IE and IE = IB + IC, the common-base relation becomes IC = [α/(1 − α)]IB + ICBO/(1 − α). Therefore the missing term is ICBO.
Correct answer: ICBO- A. Oscillators
- B. Rectifiers
- C. Amplifiers
- D. None of the above
Explanation: Negative feedback is most commonly used in amplifiers to stabilize gain, reduce distortion and noise, and increase bandwidth.
Correct answer: Amplifiers- A. equal to 1
- B. more than 10
- C. more than 100
- D. less than 1
Explanation: A common-collector amplifier, or emitter follower, has voltage gain close to but slightly less than unity.
Correct answer: less than 1- A. common base
- B. common collector
- C. common emitter
- D. none of the above
Explanation: The common-emitter configuration provides both substantial current gain and voltage gain, so its voltage gain is generally the highest…
Correct answer: common emitter- A. Resistive
- B. Capacitive
- C. Inductive
- D. None of the above
Explanation: Feedback networks in basic transistor amplifiers are commonly made with resistors because resistive dividers can sample and return a…
Correct answer: Resistive- A. common emitter
- B. common base
- C. common collector
- D. none of the above
Explanation: The common-emitter configuration has appreciable voltage gain and current gain, so their product gives the highest power gain among the…
Correct answer: common emitter- A. common emitter
- B. common collector
- C. common base
- D. none of the above
Explanation: The common-collector circuit has the highest input impedance because its input is applied at the transistor base and its emitter follower…
Correct answer: common collector- A. 1
- B. less than 1
- C. between 20 and 500
- D. above 500
Explanation: The common-emitter current gain β is normally much greater than unity and commonly falls in the range of about 20 to 500.
Correct answer: between 20 and 500- A. 500
- B. 100
- C. 1000
- D. 5000
Explanation: For strong negative feedback, the closed-loop voltage gain is approximately 1/β.
Correct answer: 100- A. Resonant
- B. Open loop
- C. Closed loop
- D. None of the above
Explanation: Feedback changes the amplifier’s overall gain from its open-loop value to the gain measured with the feedback loop closed.
Correct answer: Closed loop- A. recombine in the base
- B. recombine in the emitter
- C. pass through the base region to the collector
- D. none of the above
Explanation: The emitter is heavily doped so it injects a large number of majority carriers into the thin, lightly doped base.
Correct answer: pass through the base region to the collector- A. 25%
- B. 20%
- C. 35 %
- D. 5%
Explanation: Since IE = IC + IB and β is commonly around 20 or more, the base current is only a small fraction of emitter current, typically about 5%…
Correct answer: 5%