Patent ID: 7602248
Filing Date: 2009-10-13
Classification: H03F

Abstract:
1. A power amplifier comprising a pre-driver which amplifies the voltage of an input signal to a desired level; a driver which amplifies the power of an output signal of the pre-driver to a desired level; and an idling current setting circuit which sets the idling current of the driver: the pre-driver includes a differential pair constituted of at least two transistors, and a current mirror circuit for receiving an output of the pre-driver as a single output in double end configuration; the driver includes a push pull output transistor connected from a single output point of the pre-driver; and the idling current setting circuit includes a current setting transistor connected to the output transistor of the driver in current mirror form, a plurality of current setting resistors, a switch for switching to any of the plurality of current setting resistors, and a resistor of a high resistance value connected to a gate of the output transistor.