Free Electronics and Devices MCQs with Answers

• A. 165
• B. 165 x 10^4
• C. 100
• D. None of the above

Explanation: For an amplifier, power gain is the product of voltage gain and current gain, so voltage gain = 16500/100 = 165.

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

Explanation: For DC, the coupling capacitor prevents collector current from flowing through the load resistance RL.

• A. Sum of a.c. and d.c.
• B. c. only
• C. c. only
• D. difference of a.c. and d.c.

Explanation: The instantaneous current in a transistor branch is the sum of its steady DC component and the varying AC component: i = I_DC + i_ac.

• A. 180o
• B. 0o
• C. 90o
• D. 270o

Explanation: In a CE amplifier, an increase in input voltage increases collector current and the voltage drop across RC, causing collector output…

• A. 20 V
• B. 5 V
• C. 2 V
• D. 10 V

Explanation: At collector cutoff, collector current is zero, so there is no voltage drop across the collector resistor.

• A. Coupling
• B. Bypass
• C. Leakage
• D. None of the above

Explanation: The input capacitor transfers the AC signal to the transistor while blocking DC bias from the source, so it is a coupling capacitor.

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

Explanation: The AC load is RC in parallel with RL, which is smaller than the DC load RC alone.

• A. Two transistors
• B. One transistor
• C. Three transistor
• D. None of the above

Explanation: A single-stage transistor amplifier has one amplifying transistor; its biasing, coupling, and other components are called associated…

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

Explanation: A high input impedance draws little current from the preceding signal source and prevents excessive loading.

• A. Saturation point
• B. Cut off point
• C. Operating point
• D. None of the above

Explanation: The intersection of the d.c. load line and a.c. load line gives the quiescent or operating point, which defines the transistor's condition…

• A. 20 kΩ
• B. 2 kΩ
• C. 10 kΩ
• D. 5 kΩ

Explanation: Input impedance is found from Ohm's law: Z = V/I = 10 V / 0.002 A = 5000 Ω, or 5 kΩ.

• A. 1:1 ratio
• B. Step-up
• C. Step-down
• D. None of the above

Explanation: A power amplifier's output transformer is generally step-down to reduce the high transistor-side voltage and provide the larger current…

• A. Burning of transistor
• B. Hum in the circuit
• C. Excessive forward voltage
• D. None of the above

Explanation: Pulsating d.c. contains ripple at the supply frequency, which can couple into the audio signal and produce an audible hum.

• A. Amplitude
• B. Intermodulation
• C. Frequency
• D. None of the above

Explanation: A non-flat gain-frequency response amplifies some frequencies more than others, producing frequency distortion.

• A. 1V
• B. 100V
• C. 20V
• D. 10V

Explanation: Using the transistor power limit, P = V_C I_C, the maximum voltage is V_C = 1 W / 0.1 A = 10 V.

• A. 20%
• B. 80%
• C. 40%
• D. 50%

Explanation: Collector efficiency is the a.c. output power divided by the d.c. input power; here η = 2/5 × 100 = 40%.

• A. Class A power amplifier
• B. Push-pull amplifier
• C. Class C amplifier
• D. None of the above

Explanation: The driver stage normally uses a Class A amplifier because it provides good linearity and supplies the signal power needed to drive the…

• A. 1 W
• B. 2 W
• C. 4 W
• D. None of the above

Explanation: For r.m.s. values, output power is P = V_rms I_rms = 5 × 0.2 = 1 W. No power factor is specified, so unity power factor is assumed for the…

• A. 10 W
• B. 15 W
• C. 5 W
• D. 20 W

Explanation: A transformer-coupled Class A amplifier has a maximum theoretical efficiency of 50%, so producing 10 W of a.c.

• A. 20 W
• B. 40 W
• C. 10 W
• D. 80 W

Explanation: At the worst-case dissipation point in a Class B push-pull stage, each transistor dissipates about 0.2 times the maximum a.c.