The three-dimensional heat conduction equation for steady state operating conditions of bipolar microwave power transistors has been solved.Based on the principle of thermal-electric feedback

the nonuniform distribution of current and juc-tion temperature in bipolar microwave power transistors have been calculated

the effects of the collector bias voltage and emitter ballast resistors on this distributions have been discussed quantitively

and a ballast technique of the unequal values of the resistors has been presented.The experiments have shown that the use of this technique in microwave power transistors has given rise to a considerable improvements in uniform distribution of junction temperature and current.