Provided is an enhanced switching speed photo-coupler circuit for providing an output signal in response to an isolated input signal. The photocoupler is comprised of a phototransistor which operates in the active region in response to an applied input signal. A switching transistor connected to the output of the phototransistor is turned on when the phototransistor enters the active region. An output signal, measured from the collector of the switching transistor, will change only slightly in comparison with the off state. In one embodiment, a power semiconductor is coupled to the circuit output for enhanced switching speed.