Free Electronics and Devices MCQs with Answers

• A. 2.3mA
• B. 3.2mA
• C. 4.6 mA
• D. 5.2mA

Explanation: Using IC = α(IB + IC) + ICO gives IC = (αIB + ICO)/(1 − α) = (0.98 × 100 μA + 6 μA)/0.02 = 5.2 mA.

• A. 2
• B. 1
• C. 1/2
• D. 0

Explanation: CMRR = Ad/Ac, and 80 dB means a gain ratio of 10^(80/20) = 10,000. Therefore, Ac = 20,000/10,000 = 2.

• A. current controlled capacitor
• B. voltage controlled capacitor
• C. current controlled inductor
• D. voltage controlled inductors

Explanation: The MOSFET gate controls the channel through an electric field, so its effective capacitance varies with applied voltage.

• A. Common base
• B. Common emitter
• C. Common collector
• D. All have the same gain

Explanation: The common-emitter configuration provides both substantial voltage gain and current gain, so its power gain is generally the highest of…

• A. cut off point
• B. saturation point
• C. operating point
• D. quasi saturation point

Explanation: The horizontal intercept occurs when collector current is zero and the full supply voltage appears across the transistor, which is the…

• A. 99%
• B. 85%
• C. 50%
• D. 25%

Explanation: For a class-A common-base amplifier with a resistive collector load, the maximum theoretical efficiency is 25%.

• A. Only the temperature
• B. only the β of the transistor
• C. Both Temperature & β
• D. None of the above

Explanation: The emitter resistor creates negative feedback: it counteracts changes in collector current caused by temperature or transistor beta…

• A. Vdc = Vm/π, PIV=2Vm
• B. Vdc = 2Vm/π, PIV=2vm
• C. Vdc = 2Vm/π, PIV=Vm
• D. Vdc = Vm/π, PIV=Vm

Explanation: For a center-tapped full-wave rectifier, the average load voltage is 2Vm/π, and the nonconducting diode must withstand twice the peak…

• A. Current controlled Current source
• B. Current controlled voltage source
• C. Voltage controlled voltage source
• D. voltage controlled current source

Explanation: The JFET gate voltage controls the channel current, while the drain-source path acts as the output port.

• A. Internal Capacitance of the device
• B. Coupling capacitor at the input
• C. Skin effect
• D. Coupling capacitor at the output

Explanation: At high frequencies, the transistor's internal junction and stray capacitances provide low-reactance paths that reduce gain.

• A. Transistor capacitances
• B. High current effects in the base
• C. Parasitic inductive elements
• D. The early effect

Explanation: Internal transistor capacitances, especially base-emitter and base-collector capacitances, increasingly shunt the signal as frequency…

• A. Reduces gain
• B. Increase frequency &phase distortion
• C. Reduces bandwidth
• D. Increases noise

Explanation: Negative feedback sacrifices some amplifier gain but generally increases bandwidth and reduces distortion and noise.

• A. get maximum efficiency
• B. remove even harmonics
• C. overcome a crossover distortion
• D. reducing collector dissipation

Explanation: Class B amplifiers suffer crossover distortion near zero current, where neither transistor conducts properly.

• A. 0.25
• B. 0.5
• C. 0.75
• D. 1

Explanation: Using the Shockley relation, the factor is 1 - VGS/Vp = 1 - (-2/-4) = 0.5. Since gm0 = 2IDSS/|Vp| = 1 mA/V, gm = 1 × 0.5 = 0.5 mA/V.

• A. Gate voltage
• B. Drain voltage
• C. Source voltage
• D. Body voltage

Explanation: Increasing drain voltage enlarges the drain depletion region, causing channel-length modulation and shortening the effective channel…

• A. fast turn-on
• B. fast turn-off
• C. large collector-base reverse bias
• D. large emitter-base forward bias

Explanation: The Early effect occurs when increased collector-base reverse bias widens the base depletion region and effectively narrows the base…

• A. the amplitude of output is proportional to rate of change of input
• B. the amplitude of output is proportional to input
• C. output occurs when input is finite and constant
• D. polarity of input and output is the same

Explanation: An op-amp differentiator produces an output proportional to the time derivative of the input, so faster input changes produce a larger…

• A. all resistors
• B. all transistors
• C. all inductors
• D. all capacitors

Explanation: For the usual midband AC equivalent circuit, capacitors have negligible reactance and are replaced by short circuits.

• A. negligible input resistance and high output resistance
• B. high input resistance and low output resistance
• C. medium input resistance and high output resistance
• D. low input resistance as well as output resistance

Explanation: A common-emitter transistor stage has moderate input resistance and relatively high output resistance, along with useful voltage and…

• A. doping of base
• B. size of emitter
• C. rating of transistor
• D. temperature

Explanation: Transistor leakage current is strongly temperature-dependent and increases significantly as temperature rises.