Common base

In electronics, a common-base (also known as grounded-base) amplifier is one of three basic single-stage bipolar junction transistor (BJT) amplifier topologies, typically used as a current buffer or voltage amplifier. In electronics, a common-base (also known as grounded-base) amplifier is one of three basic single-stage bipolar junction transistor (BJT) amplifier topologies, typically used as a current buffer or voltage amplifier. In this circuit the emitter terminal of the transistor serves as the input, the collector as the output, and the base is connected to ground, or 'common', hence its name. The analogous field-effect transistor circuit is the common-gate amplifier. As current is sunk from the emitter, this provides potential difference so causing the transistor to conduct. The current conducted via the collector is proportional to the voltage across the base–emitter junction, accounting for the bias, as with other configurations.