Free Electronics and Devices MCQs with Answers

• A. Increase in both input & output impedances
• B. Decreases in both input & output impedances
• C. Increase in input impedance & decreases in output impedance
• D. Decrease in input impedance & increase in output impedance

Explanation: Voltage-series feedback mixes the feedback voltage in series at the input, increasing input impedance, and samples output voltage in…

• A. resistor between source and load
• B. inductor between source and load
• C. capacitor between source and load
• D. either A. or B.

Explanation: A coupling capacitor passes AC while blocking DC, so it prevents a DC return path between the source and load.

• A. gm r0
• B. gm / r0
• C. gm rπ
• D. gm /rπ

Explanation: For a BJT, the small-signal current gain is approximately β = gm rπ, since gm relates collector current to base-emitter voltage and rπ…

• A. 1/11KΩ
• B. 1/5KΩ
• C. 5KΩ
• D. 11KΩ

Explanation: Current-shunt feedback reduces input resistance by the factor 1 + Aβ. Here 1 + Aβ = 1 + 50(0.2) = 11, so the new input resistance is 1…

• A. 23dB
• B. 25dB
• C. 46dB
• D. 50dB

Explanation: The common-mode rejection ratio in decibels is the differential voltage gain minus the common-mode voltage gain: CMRR = 48 − 2 = 46 dB.

• A. CB arrangement with output shorted
• B. CC arrangement with output shorted
• C. CE arrangement with output shorted
• D. None of the above

Explanation: In the CE h-parameter model, h_ie is the input impedance measured with the output terminals short-circuited.

• A. The same as for CB
• B. The same as for CC
• C. Different from that in CB
• D. None of the above

Explanation: Although every transistor configuration uses four h parameters, their numerical values depend on whether the circuit is CB, CE, or CC.

• A. Voltage gain
• B. Current gain
• C. Input impedance
• D. None of the above

Explanation: The parameter h_fe is the forward current gain in the common-emitter configuration with the output port short-circuited.

• A. May or may not change
• B. Do not change
• C. Also change
• D. None of the above

Explanation: Transistor h parameters depend on operating conditions, including temperature, because temperature changes carrier behavior and junction…

• A. Also change
• B. Do not change
• C. May or may not change
• D. None of the above

Explanation: h parameters are small-signal quantities evaluated at a particular bias or operating point.

• A. Mho
• B. Ohm
• C. Farad
• D. None of the above

Explanation: h_ie is an input impedance, defined as a voltage-to-current ratio, so its unit is the ohm.

• A. Two
• B. Four
• C. Three
• D. None of the above

Explanation: A transistor two-port network has four hybrid parameters: h_i, h_r, h_f, and h_o.

• A. Small signals only
• B. Large signals only
• C. Both small and large signals
• D. None of the above

Explanation: A transistor can be linearized around its bias point only for small signal variations.

• A. Large signals only
• B. Small signals only
• C. Both small and large signals
• D. None of the above

Explanation: The h-parameter equivalent circuit is obtained by linearizing the transistor around its operating point, so it is accurate for small…

• A. Mixed
• B. Single
• C. Unique
• D. None of the above

Explanation: Hybrid means mixed or made from different types. In transistor h parameters, the term refers to the mixture of impedance, admittance…

• A. Input
• B. Output
• C. Input as well as output
• D. None of the above

Explanation: For h_ie and h_fe, the output voltage is set to zero, which means the output port is a.c. short-circuited.

• A. Hie
• B. Hoe
• C. Hre
• D. None of the above

Explanation: In the common-emitter arrangement, h_ie represents the input impedance when the output is a.c. short-circuited.

• A. 50 KHz
• B. 100KHz
• C. 1000/17 KHz
• D. 1000/7.07 KHz

Explanation: A 20 dB voltage gain corresponds to a voltage gain of 10, since 20 log₁₀(A_v) = 20. Thus the bandwidth is approximately 1 MHz/10 = 100 kHz.

• A. input voltage dependent linear transfer characteristic
• B. high voltage gain
• C. high input resistance
• D. high CMRR

Explanation: A differential amplifier rejects signals common to both inputs while amplifying their difference, giving it a high common-mode rejection…

• A. Q -factor of the tuned o/p circuit
• B. Q -factor of the tuned i/p circuit
• C. Quiescent operating point
• D. Q-factor of the o/p and i/p circuits as well as quiescent operating point

Explanation: For the usual RF tuned amplifier, bandwidth is inversely proportional to the Q-factor of its tuned output circuit, approximately BW =…