Transistors — Part 1 MCQs with Explanations

A transistor is a current-operated device. In a transistor, the output current is controlled by the input current, specifically the base current controls the collector current. This characteristic makes it a current-controlled device, unlike some other devices that are controlled by voltage.

The correct answer is Is lowered . In a double-tuned circuit , the mutual inductance between the two tuned circuits determines the coupling between them. If the mutual inductance is decreased , the coupling between the circuits is weakened, resulting in a lower peak of the resonance curve. This happens because reduced coupling limits the transfer of energy between the circuits, thereby lowering the amplitude of the resonance. The other options do not accurately describe the effect of decreased mutual inductance on the resonance curve.

For germanium transistor amplifier , the voltage across the collector-emitter junction ( VCE ) should not fall below 0.7 V for faithful amplification. This condition ensures that the transistor remains in the active region of operation, where it exhibits linear amplification characteristics. When VCE drops below approximately 0.7 V for a germanium transistor, the transistor enters the saturation region, causing distortion and non-linear amplification. Therefore, to achieve faithful amplification in a germanium transistor amplifier, Option C: Not fall below 0.7 V is the correct requirement for VCE .

In a transistor, particularly in an NPN transistor, the base current (IB) is primarily due to the movement of electrons. The base region of an NPN transistor is lightly doped and very thin, and it lies between the emitter and collector. When the emitter-base junction is forward biased, electrons from the emitter (which is heavily doped with electrons) are injected into the base. Most of these electrons pass through to the collector, but a small portion recombines with holes in the base. The movement of these electrons constitutes the base current (IB). Thus, IB is made up of electron flow, making it an electron current. Option B: hole current – Not correct in the case of NPN transistor base current. Option C and D: donor or acceptor ion currents – These refer to immobile charges in the semiconductor lattice and do not contribute to conduction current. Therefore, the correct and most accurate description is that IB is an electron current.

A transistor has two pn junctions. In a bipolar junction transistor (BJT), which is the most common type, there are two pn junctions: one between the emitter and the base, and another between the base and the collector. These two junctions are crucial for the transistor's operation, allowing it to amplify or switch electronic signals. Transistors do not have one, three, or four pn junctions; the correct number is two.

ICEO is the correct answer to “IC = [a/(1 - a)] IB + [. . . . . . . . /(1 - a)]”. This question is standard in competitive examination syllabi for Transistors.

low resistance to high resistance is the correct answer to “In a transistor, signal is transferred from a ___________ circuit”. This question is standard in competitive examination syllabi for Transistors.

ICBO is the correct answer to “IC = aIE + ___________”. This question is standard in competitive examination syllabi for Transistors.

VBE is the correct answer to “In a transistor amplifier circuit VCE = VCB + ___________”. This question is standard in competitive examination syllabi for Transistors.

Less than is the correct answer to “The stability factor of a collector feedback bias circuit is ___________ that of base resistor bias.”. This question is standard in competitive examination syllabi for Transistors.

$$\beta + 1$$ is the correct answer to “The value of stability factor for a base resistor bias is ___________.”. This question is standard in competitive examination syllabi for Transistors.

Decreases is the correct answer to “When either L or C is increased, the resonant frequency of LC circuit ___________”. This question is standard in competitive examination syllabi for Transistors.

Is increased is the correct answer to “If L/C ratio of a parallel LC circuit is increased, the Q of the circuit ___________”. This question is standard in competitive examination syllabi for Transistors.

Is decreased is the correct answer to “If the resistance of a tuned circuit is increased, the Q of the circuit ___________”. This question is standard in competitive examination syllabi for Transistors.

pass through the base region to the collector is the correct answer to “Most of the majority carriers from the emitter ___________”. This question is standard in competitive examination syllabi for Transistors.

remain the same is the correct answer to “A transistor is connected in CB mode. If it is not connected in CE mode with same bias voltages, the values of IE, IB and IC will ___________”. This question is standard in competitive examination syllabi for Transistors.

Change in ICBO is the correct answer to “When the temperature changes, the operating point is shifted due to .”. This question is standard in competitive examination syllabi for Transistors.

silicon is the correct answer to “BC 147 transistor indicates that it is made of ___________”. This question is standard in competitive examination syllabi for Transistors.

IF is the correct answer to “Double tuned circuits are used in ___________ stages of a radio receiver”. This question is standard in competitive examination syllabi for Transistors.

200 is the correct answer to “In a tansistor, IC = 100 mA and IE = 100.2 mA. The value of ß is ___________”. This question is standard in competitive examination syllabi for Transistors.

90 is the correct answer to “If the value of a is 0.9, then value of ß is ___________”. This question is standard in competitive examination syllabi for Transistors.

Is sensitive to changes in ß is the correct answer to “The disadvantage of base resistor method of transistor biasing is that it ___________”. This question is standard in competitive examination syllabi for Transistors.

Ohm is the correct answer to “The dimensions of L/CR are that of ___________”. This question is standard in competitive examination syllabi for Transistors.

5% is the correct answer to “In a transistor, the base current is about ___________ of emitter current”. This question is standard in competitive examination syllabi for Transistors.

Equal to but opposite in phase to is the correct answer to “At series resonance, voltage across L is ___________ voltage across C”. This question is standard in competitive examination syllabi for Transistors.

Proper direct current is the correct answer to “Transistor biasing is done to keep ___________ in the circuit”. This question is standard in competitive examination syllabi for Transistors.

Radio frequency is the correct answer to “A tuned amplifier is used in ___________ applications”. This question is standard in competitive examination syllabi for Transistors.

common emitter is the correct answer to “The most commonly used transistor arrangement is ___________ arrangement”. This question is standard in competitive examination syllabi for Transistors.

d.c. is the correct answer to “Transistor biasing represents ___________ conditions”. This question is standard in competitive examination syllabi for Transistors.

Minimum is the correct answer to “At series resonance, the circuit offers ___________ impedance”. This question is standard in competitive examination syllabi for Transistors.

Class C is the correct answer to “A tuned amplifier is generally operated in ___________ operation”. This question is standard in competitive examination syllabi for Transistors.

Loose is the correct answer to “If a high degree of selectivity is desired, then double-tuned circuit should have ___________ coupling”. This question is standard in competitive examination syllabi for Transistors.

L and C is the correct answer to “A resonant circuit contains ___________ elements”. This question is standard in competitive examination syllabi for Transistors.

$${{\text{I}}_{{\text{CEO}}}}$$ is the correct answer to “$${{\text{I}}_{\text{C}}} = \beta \,{{\text{I}}_{\text{B}}}\, + \,........$$”. This question is standard in competitive examination syllabi for Transistors.

Not fall below 0.7 V is the correct answer to “For faithful amplification by a transistor circuit, the value of VBE should ___________ for a silicon transistor”. This question is standard in competitive examination syllabi for Transistors.

1 is the correct answer to “An ideal value of stability factor is ___________”. This question is standard in competitive examination syllabi for Transistors.

10% is the correct answer to “At series or parallel resonance, the circuit power factor is ___________”. This question is standard in competitive examination syllabi for Transistors.

$$\beta = \frac{\alpha }{{1 - \alpha }}$$ is the correct answer to “The relation between $$\beta $$ and $$\alpha $$ is ___________.”. This question is standard in competitive examination syllabi for Transistors.

Decreases is the correct answer to “If Q of an LC circuit increases, then bandwidth ___________”. This question is standard in competitive examination syllabi for Transistors.

IE = IC + IB is the correct answer to “In a transistor ___________”. This question is standard in competitive examination syllabi for Transistors.