RF power amplifier with load insensitive indirect forward power detector

摘要

A power amplifier circuit includes an adjustable gain power amplifier for amplifying an RF input signal. An isolated node in the adjustable gain power amplifier is isolated from the output load by a gain stage of the adjustable gain power amplifier. The power level of a signal at the isolated node corresponds to the power level of a signal at the output load. A detector is either capacitively coupled to the isolated node or connected by a direct current (DC) connection. The detector detects the power level of the signal at the isolated node. The detector generates a power level indicator that is sent to a gain control circuit. The gain control circuit adjusts the gain of the adjustable gain power amplifier to maintain a constant drive level at the isolated node.