Common gate

Figure 1: Basic N-channel common-gate circuit (neglecting biasing details); current source ID represents an active load; signal is applied at node Vin and output is taken from node Vout; output can be current or voltage

In electronics, a common-gate amplifier is one of three basic single-stage field-effect transistor (FET) amplifier topologies, typically used as a current buffer or voltage amplifier. In this circuit, the source terminal of the transistor serves as the input, the drain is the output, and the gate is connected to some DC biasing voltage (i.e. an AC ground), or "common," hence its name. The analogous bipolar junction transistor circuit is the common-base amplifier.