Free Electronics and Devices MCQs with Answers

• A. RC coupling
• B. Transformer coupling
• C. Direct coupling
• D. Impedance couplingLearn Quantum Physics

Explanation: The final stage usually drives a low-resistance load, so transformer coupling is used for impedance matching and efficient power transfer.

• A. There is considerable power loss
• B. There is hum in the output
• C. Electrical size of coupling capacitor becomes very large
• D. None of the aboveCompare Home Electronics

Explanation: At extremely low frequencies, the capacitor must have a very large capacitance to keep its reactance small.

• A. Power loss in the coupling device
• B. Loading effect of the next stage
• C. The use of many transistors
• D. The use of many capacitorsSource Electronic Components

Explanation: The next amplifier stage loads the preceding stage, reducing its effective output and hence the overall gain.

• A. 3 db
• B. 66 db
• C. 20 db
• D. 200 db

Explanation: Current gain in decibels is 20 log10(Ai), so 20 log10(2000) is approximately 66 dB.

• A. Block a.c.
• B. Separate bias of one stage from another
• C. Increase thermal stability
• D. None of the above

Explanation: RC and transformer coupling transfer the AC signal while preventing the DC bias of one stage from disturbing the bias of the next stage.

• A. 1 µF
• B. 100 pF
• C. 0.01 µF
• D. 50 µF

Explanation: The emitter bypass capacitor in a multistage amplifier is commonly around 50 µF, providing a low-reactance path for AC emitter current…

• A. Large value of coupling capacitor
• B. Low efficiency
• C. Large number of components
• D. None of the above

Explanation: RC-coupled amplifiers waste considerable power in the collector resistor, so their efficiency is low and they are mainly used for…

• A. It is a simple unit
• B. Calculations become easy
• C. Human ear response is logarithmic
• D. None of the above

Explanation: Decibels use a logarithmic scale, which corresponds approximately to the logarithmic response of human hearing over a wide range of sound…

• A. Good
• B. Very good
• C. Excellent
• D. Poor

Explanation: Transformer coupling has a poor frequency response because transformer inductance and winding capacitance affect low- and high-frequency…

• A. 50%
• B. 35%
• C. 26%
• D. 22%

Explanation: A 1 dB power ratio is 10^(1/10) ≈ 1.259, corresponding to about a 26% increase in power. Thus option c is the closest value.

• A. Sideband
• B. Resonant
• C. Half-resonant
• D. Half-power

Explanation: At each cutoff frequency, the output power falls to half its midband value, or the voltage falls to 0.707 of its maximum.

• A. Collector voltage is stepped up
• B. resistance is low
• C. collector voltage is stepped down
• D. none of the above

Explanation: The transformer winding has very low DC resistance, so little power is lost as heat compared with a collector resistor.

• A. 0
• B. 1
• C. 1
• D. 10

Explanation: An ideal amplifier adds no noise, so its noise factor is 1 in ratio form and 10 log₁₀(1) = 0 dB.

• A. Power
• B. Voltage
• C. Current
• D. None of the above

Explanation: Transformer coupling is mainly used in power amplifiers because the transformer transfers maximum AC power and provides impedance matching…

• A. Good impedance matching
• B. Economy
• C. High efficiency
• D. None of the above

Explanation: RC coupling is economical because resistors and capacitors are inexpensive, compact, and require no magnetic core.

• A. Changes abruptly with frequency
• B. Is constant
• C. Changes uniformly with frequency
• D. None of the above

Explanation: In the mid-frequency range, the coupling and bypass capacitors act nearly as short circuits while transistor parameters remain fairly…

• A. Voltage
• B. Current
• C. Power
• D. None of the above

Explanation: RC coupling is used for voltage amplification because it offers a fairly flat mid-band frequency response and good signal fidelity.

• A. One stage
• B. Two stages
• C. Three stages
• D. More than one stages

Explanation: A radio receiver normally uses several stages, such as RF amplification, mixing, IF amplification, detection, and audio amplification.

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

Explanation: For DC analysis, the emitter and collector currents are approximately equal, so the supply sees the series resistance RC + RE.

• A. CC
• B. CB
• C. CE
• D. none of the above

Explanation: The common-emitter configuration provides both substantial current gain and voltage gain, giving it the highest power gain among the three…