Dual-gate MESFET variable gain constant output power amplifier

摘要

A variable-gain, constant output power amplifier which generates an output rf signal of constant power level in response to an input rf signal of varying power level. The amplifier gain is preadjusted by a plurality of feedforward automatic-gain-control circuits to provide the constant output power. The amplifier comprises five dual-gate MESFET signal-amplifying stages. The first and last stages do not have built-in automatic-gain-control. The first stage is provided for preamplification prior to sampling the input signal, and the last stage is provided for setting the level of the output power externally. The signal at the input of each of the middle three stages is sampled through a coupler and detected and processed at video frequencies to dynamically preadjust the gain of the next signal-amplifying stage.