Temperature compensating method and apparatus for thermally stabilizing

Abstract

The amplifier device, which may be an FET power amplifier, is of the type having an operating parameter which exhibits thermal instability under constant electrode bias conditions, and thermal stability when bias is varied as a function of ambient temperature in accordance with an empirically determined relationship. The method involves the empirical determination of the varying bias conditions needed to cause thermal stability of the operating parameter over the required range of temperatures, and the provision of a temperature-compensating power supply which produces the necessary bias at each temperature in the range. The temperature-compensating power supply incorporates a bias monitor circuit to produce a control signal which has a nearly constant value so long as bias conditions are in accordance with the empirically determined relationship at every temperature within the range. However, if bias deviates from the predetermined relationship, the control signal also deviates, such that control signal deviations are a monotonic function of bias deviations. The power supply is provided with a feedback-control circuit which responds to the control signal deviations by adjusting the output magnitude of the supply to agree with the predetermined relationship.