There are provided a bias circuit and a power amplifier. The bias circuit includes a first temperature compensating unit connected between an operating voltage terminal and a ground and operating according to a reference voltage to generate a turn-on voltage, a second temperature compensating unit connected between a reference voltage terminal and the ground and operating according to the turn-on voltage to generate a control voltage, a power mode selecting unit selecting one of a high power mode and a low power mode and providing an additional current to the first temperature compensating unit at the time of selecting the low power mode to increase the turn-on voltage, and a bias voltage generating unit generating a bias voltage according to the control voltage, wherein the control voltage and the bias voltage are decreased according to the increase in the turn-on voltage.