BJT - Quiz

In a BJT, which of the following regions is the thinnest?

• Base
• Collector
• Emitter
• Depletion region

Answer explanation

The base is the thinnest region in a BJT to allow easy diffusion of carriers.

What is the main function of the emitter in a BJT?

• To collect majority carriers
• To control the current flow
• To inject majority carriers into the base
• To increase the breakdown voltage

Answer explanation

The emitter injects majority carriers into the base to enable transistor action.

In an NPN transistor operating in active mode, the base-emitter junction is:

• Reverse biased
• Forward biased
• Open circuit
• Short circuit

Answer explanation

In active mode, the base-emitter junction is forward biased.

The current gain (β) of a BJT is given by:

• β = I_B / I_C
• β = I_C / I_E
• β = I_C / I_B
• β = I_E / I_B

Answer explanation

Current gain β is the ratio of collector current to base current.

In the saturation region of a BJT, the collector-emitter voltage (V_CE) is:

• Maximum
• Zero
• Very small but not zero
• Negative

Answer explanation

In saturation, V_CE is small but not zero as the transistor is fully conducting.

The Early effect in a BJT refers to:

• Increase in base width with increasing collector voltage
• Decrease in base width with increasing collector voltage
• Increase in collector current due to base widening
• Thermal breakdown due to excessive current

Answer explanation

The Early effect is the decrease in base width due to an increase in V_CE.

In a common-emitter amplifier, the phase shift between input and output voltage is:

• 0°
• 90°
• 180°
• 270°

Answer explanation

A common-emitter amplifier inverts the signal, resulting in a 180° phase shift.

The purpose of biasing a BJT is to:

• Minimize power consumption
• Keep the transistor in the desired operating region
• Reduce the base current
• Increase the breakdown voltage

Answer explanation

Biasing keeps the transistor in the desired operating region for proper function.

A BJT is said to be in the cutoff region when:

• Both junctions are forward biased
• Both junctions are reverse biased
• The base-emitter junction is forward biased and the base-collector junction is reverse biased
• The collector current is at its maximum

Answer explanation

A BJT is in cutoff when both junctions are reverse biased, leading to no current flow.

The common-base current gain (α) of a BJT is related to β by:

• α = β + 1
• α = 1 - β
• α = β / (1 + β)
• α = 1 / β

Answer explanation

The relationship between α and β is α = β / (1 + β).