Question

The early-effect in a BJT is caused by

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

Hint:

Think of the Early Effect as the collector "reaching into" the base. A larger reverse voltage on the collector gives it a longer "reach" (wider depletion region), which makes the base effectively narrower.

Answer 1

The Correct Option is C

Step 1: Define the Early Effect.The Early effect, also termed base-width modulation, refers to the change in the effective base width of a Bipolar Junction Transistor (BJT) resulting from variations in the collector-base junction voltage. This modulation of the base width influences both the collector current and the transistor's output characteristics.
Step 2: Examine the collector-base junction.When the transistor operates in the active region, the collector-base junction experiences reverse bias, leading to the formation of a depletion region at the junction.
Step 3: Relate reverse bias to base width.Increasing the reverse bias voltage across the collector-base junction expands the depletion region. This expansion encroaches upon both the collector and the base, effectively shrinking the neutral base width. This phenomenon constitutes the Early effect, driven by the collector-base reverse bias.