Common Drain MOSFET Amplifier Calculator

Common Drain MOSFET Amplifier Calculator

Calculate the small-signal voltage gain of a common drain (source follower) MOSFET amplifier.

Step 1: Enter Circuit Parameters

Example: \(0.002\) S (2 mS)

Enter the effective source resistance (if bypassed, \(R_S\) ≈ 0 and gain ≈ 1)

With \(R_S = 0\) (bypassed): $$ A_v = g_m \, R_D \quad (\text{Note: For common drain, if source is bypassed, gain ≈ 1}) $$

With \(R_S > 0\): $$ A_v = \frac{g_m \, R_D}{1 + g_m \, R_S} $$

For a common drain (source follower) amplifier, the gain is typically slightly less than unity.