Common drain - Definition and Overview

A common-drain amplifier is one of the common configurations of FET electronic amplifier.

Characteristics

Inherent voltage gain:

<math>

g_m (R_S || R_{load}) \over 1 + g_m (R_S || R_L) <math>

Input resistance:

<math>

R_1 || R_2 <math>

Current gain:

<math>

A_{vm} {r_{in} \over R_{load}} <math>

Output resistance:

<math>

R_S || {1 \over g_m} <math>

Transistor amplifiers

• Common emitter
• Common collector
• Common base
• Common source
• Common drain
• Common gate