Common source - Definition and Overview

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

Characteristics

Inherent voltage gain:

With C_S:

<math>

-g_m (R_D || R_{load}) <math>

Without C_S:

<math>

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

Input resistance:

<math>

R_1 || R_2 <math>

Current gain:

<math>

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

Output resistance:

<math>

R_D <math>

Transistor amplifiers

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