Gain stability arrangement for HV MOSFET power amplifier

摘要

A high power radio frequency amplifier employs a power stage in which a bank of push-pull stages are connected in parallel. These power stages employ relatively low-cost high voltage MOSFETs. Because the devices are operated in their active regions, these MOSFETs are susceptible to drops in gain during operation due to heating of the transistor die. The gain fluctuation has a first, slower component that varies over a time of several minutes, and a second, faster component that varies over a span of seconds. The amplifier has B+ or drain voltage control to compensate for short-term (minutes) gain degradation and preamplifier gate voltage control to compensate for short-term (seconds) gain degradation.