Controlling the drain voltages of a two-stage FET rf amplifier to control the ouput level and improve efficiency

摘要

A dual drain control uses a variable voltage supply on the drains of a first stage (302) and a second stage (304) to control the output power. In particular, dual drain control having a 1:1 ratio is employed at lower power levels, with single drain control at higher power levels. Such drain control could use signals from a microprocessor, or a specific circuit (203) to generate the drain voltages based upon a control voltage. Use in a cellular telephone is described. The efficiency is improved.