Power amplifier saturation detection

摘要

In a portable radio transceiver, a power amplifier system includes a saturation detector that detects power amplifier saturation in response to duty cycle of the amplifier transistor collector voltage waveform. The saturation detection output signal can be used by a power control circuit to back off or reduce the amplification level of the power amplifier to avoid power amplifier control loop saturation.

主权项

1. A power amplifier system comprising:
a power amplifier including at least one transistor with an output transistor terminal in electrical communication with a power supply; a limiter in electrical communication with the output transistor terminal, the limiter configured to clip a positive cycle portion of a radio frequency (RF) signal output by the power amplifier and to provide a negative cycle portion of the RF signal to an averaging filter; and a comparator circuit configured to produce a saturation detection signal indicating whether the power amplifier is operating in a saturation state, the comparator circuit including a comparator in electrical communication with the averaging filter and a current source in electrical communication with the comparator.