Patent ID: 7573336

Claim:
A power amplifier, comprising a first amplification transistor for amplifying an input signal and a first bias circuit for supplying a bias current to the first amplification transistor, wherein: the first bias circuit includes: a first biasing transistor for supplying the bias current to a base of the first amplification transistor; a control input terminal to which a control input voltage is fed as a control signal for controlling amplification by the first amplification transistor; a VBE-controlled voltage source circuit; and a current mirror circuit, the VBE-controlled voltage source circuit includes: a first resistor provided between the control input terminal and a base of the first biasing transistor; a first transistor having a base connected to the first resistor and to the base of the first biasing transistor; and a second transistor having an emitter grounded, a base connected to an emitter of the first transistor, and a collector connected to the base of the first transistor, and the current mirror circuit includes: a third transistor having an emitter grounded, a base connected to the control input terminal via a second resistor, and a collector connected to the base of the third transistor via a third resistor; and a fourth transistor having an emitter grounded, a base connected to the collector of the third transistor, and a collector connected to the base of the second transistor.