Patent ID: 7288987
Filing Date: 2007-10-30
Classification: H03F

Abstract:
1. A power amplifier circuit, comprising: an input for receiving an input signal; a coupler for receiving the input signal and splitting the input signal on two signal paths; a first amplifier device coupled to the coupler on a first of the two signal paths and receiving the input signal and providing a first amplified signal, said first amplifier device having a first turn on threshold; a second amplifier device coupled to the coupler on a second of the two signal paths and receiving the input signal and providing a second amplified signal, said second amplifier device having a second turn on threshold and an impedance near zero when said input signal is below said second turn on threshold; an output load coupled to said first and second amplifier devices; a DC power supply; a first bias circuit coupled to the first amplifier device and the DC power supply and providing a first bias to the first amplifier device setting the first turn on threshold of said first amplifier device; bias control means, coupled to the second amplifier device and the DC power supply, for providing a second bias to the second amplifier device setting the second turn on threshold of said second amplifier device at a substantially higher level than said first turn on threshold, said second turn on threshold corresponding to a peak power region of the input signal; and an output coupled to the first and second amplifier devices via said output load and providing an amplified output signal.