Free Electronics and Devices MCQs with Answers

• A. more than 1
• B. less than 1
• C. 1
• D. none of the above

Explanation: The symbol is evidently alpha, the common-base current gain, defined as collector current divided by emitter current.

• A. is forward biased
• B. is reverse biased
• C. carrier more than rated current
• D. none of the above

Explanation: A zener diode can operate safely in reverse bias only up to its rated current and power.

• A. ß = 1 / (1 - a )
• B. ß = (1 - a ) / a
• C. ß = a / (1 - a )
• D. ß = a / (1 + a )

Explanation: Since α = I_C/I_E and I_E = I_C + I_B, rearranging gives β = I_C/I_B = α/(1 − α). Therefore option c is the required relation.

• A. the same as
• B. less than
• C. more than
• D. none of the above

Explanation: A zener diode is heavily doped compared with an ordinary crystal diode, producing a thin depletion region and a controlled breakdown…

• A. 180o
• B. 90o
• C. 270o
• D. 0o

Explanation: In a common-base transistor, the output collector voltage varies in phase with the input emitter voltage, so there is no phase reversal.

• A. forward characteristic
• B. doping level
• C. reverse characteristic
• D. PIC rating

Explanation: When a diode is used for rectification, it must withstand the maximum reverse voltage applied during the nonconducting half-cycle.

• A. more than
• B. less than
• C. the same as
• D. none of the above

Explanation: The CE leakage current is approximately I_CEO = (1 + β)I_CBO, so transistor current gain makes it much larger than the CB leakage current.

• A. reverse
• B. forward
• C. either reverse or forward
• D. none of the above

Explanation: A zener diode is normally operated in its reverse-breakdown region, where it maintains an approximately constant voltage.

• A. one pn junction
• B. two pn junctions
• C. three pn junctions
• D. none of the above

Explanation: A zener diode is a specially manufactured two-layer semiconductor device containing one p-n junction.

• A. germanium
• B. silicon
• C. carbon
• D. none of the above

Explanation: BC147 is a silicon NPN transistor; the BC designation is commonly used for low-power silicon transistors.

• A. decreases
• B. increases
• C. remains the same
• D. none of the above

Explanation: As temperature rises, leakage current increases and the base-emitter voltage needed for conduction falls, so the effective base-emitter…

• A. common emitter
• B. common base
• C. common collector
• D. none of the above

Explanation: The common-emitter arrangement provides useful voltage and current gain, giving it the widest general use in transistor amplifiers.

• A. reverse
• B. forward
• C. forward or reverse
• D. none of the above

Explanation: Rectification uses the diode's forward characteristic, in which current flows readily in one direction while reverse current is very…

• A. high
• B. zero
• C. low
• D. very low

Explanation: A transistor's output impedance is generally treated as high, especially in the common-emitter amplifier model, because a change in…

• A. lightly
• B. heavily
• C. moderately
• D. none of the above

Explanation: The emitter is heavily doped so it can inject a large number of majority carriers into the base.

• A. an amplifier
• B. a voltage regulator
• C. a rectifier
• D. a multivibrator

Explanation: A Zener diode is operated in its controlled reverse-breakdown region, where it maintains an approximately constant voltage across a load.

• A. applied voltage
• B. breakdown voltage
• C. forward voltage
• D. barrier potential

Explanation: The knee voltage is the approximate forward voltage at which diode current begins to rise sharply, so it is associated with the barrier…

• A. forward
• B. inverse
• C. poor
• D. reverse

Explanation: A large diode current normally occurs under forward bias, when the junction barrier is reduced and majority carriers cross the junction…

• A. remains the same
• B. decreases
• C. increases
• D. becomes zero

Explanation: Reverse leakage current increases with temperature because thermally generated minority carriers become more numerous.

• A. remains the same
• B. is increased
• C. is decreased
• D. none of the above

Explanation: Heavier doping narrows the depletion region and causes breakdown at a lower reverse voltage, especially in a Zener-type junction.