FET Small-Signal Amplification: Based on the V–I characteristics of a Field Effect Transistor (FET), identify the region in which the device should be biased for small-signal amplification.

Introduction / Context:
For FET amplifiers, proper biasing ensures linear operation with good gain. The device characteristics (drain current vs. drain–source voltage) show several distinct regions: cutoff, ohmic (linear), saturation (active), and breakdown. Amplification is only feasible in one of them.

Given Data / Assumptions:

• Typical n-channel JFET or MOSFET characteristic curve is implied.
• Regions: AB (cutoff), BC (ohmic), CD (saturation/active), BD (includes breakdown).

Concept / Approach:

The small-signal amplification region corresponds to the saturation (also called active) region, where drain current is controlled primarily by gate–source voltage and remains nearly constant over a range of drain–source voltages.

Step-by-Step Solution:

Verification / Alternative check:

Practical FET amplifier bias points are always chosen in the saturation region, validating CD as the correct choice.

Why Other Options Are Wrong:

• AB: Cutoff, no current.
• BC: Resistive behavior, not linear gain.
• BD: Beyond safe operation.

Common Pitfalls:

• Confusing MOSFET digital switching (cutoff & saturation in digital sense) with analog small-signal operation (saturation = active region).

Final Answer:

CD