Patent ID: 6897732
Filing Date: 2005-05-24
Classification: H03F

Abstract:
1. An amplifier comprising: a front amplification stage that includes a first transistor; a rear amplification stage which amplifies an output signal of said front amplification stage, said rear amplification stage being disposed immediately after said front amplification stage, said rear amplification stage including a plurality of amplification units connected in parallel, said plurality of amplification units include rear stage transistors; and a rear stage DC bias control circuit which controls a bias of a second transistor, which is one of the rear stage transistors, according to an input level of an RF signal, wherein one of the plurality of amplification units performs on/off switching of amplification operation according to the RF input of the front amplification stage or increase a bias current as the RF input increases, and said rear stage DC bias control circuit is connected between an emitter of the first transistor and a base of the second transistor and the second transistor is supplied with a bias controlled by said rear stage DC bias control circuit.