Investigation of hFE Degradation in Microwave Transistors due to E-B Breakdown Under Multicarrier Conditions

The use of RF transistor power amplifiers under multicarrier operating conditions in satellite transponders can create reliability problems incompatible with a long mission life, due to the high instantaneous voltage levels incurred, particularly in the emitter base junction. These high emitter base voltages in the reverse direction can lead to hFE degradation as the junction breakdown voltage is approached with a corresponding degradation in R.F. performance. This paper describes an RF/DC series of experiments which are used in an attempt to correlate the RF emitter base reverse voltage stress levels and consequent hEE degradation with computer predictions based upon a large signal model of the transistor.