Question

In analyzing the role of BJTs in the design of an analog signal amplifier, which of the following factors is critical for maximizing linear amplification?

• A. Ensuring the BJT is always in saturation
• B. Operating the BJT in the active region
• C. Selecting a BJT with the highest possible current gain
• D. Using a BJT with minimal base-emitter voltage

Hint:

For signal amplification, always bias the BJT in the active region — not cutoff, not saturation!

Answer 1

The Correct Option is B

For a Bipolar Junction Transistor (BJT) to function effectively as a linear amplifier, it must be biased to operate in its active region. In this region:

• The base-emitter junction is forward biased,
• The base-collector junction is reverse biased,
• The output collector current is proportional to the input base current.

This proportional behavior ensures that the transistor amplifies the input signal faithfully without distortion — a fundamental requirement for analog signal amplification.
Why the other options are incorrect:

• (A) Saturation is used in switching, not in amplification.
• (C) While higher current gain (\(\beta\)) improves amplification, linearity and controlled gain depend more critically on operating region.
• (D) Base-emitter voltage affects biasing but isn’t the primary factor for linear operation.

Thus, for maximizing linear amplification, the BJT must operate in the active region.