The Sensitivity of Microwave Bipolar Transistors and Amplifiers to Ionizing Radiation

It has been previously shown that small-signal microwave transistors are sensitive to ionizing radiation and that this can lead to application limitations . This paper extends the work to a wider range of currently used transistor types and amplifiers with applications ranging from low noise front-end to class C power output amplifiers. Two types of hEE degradation have been identified viz. "permanent and room-rtemperature current dependent "recoverable". Both types of degradation have been found throughout the range of transistor types and it is shown that they can also be simulated by avalanching the emitter-base junctions. Class A amplifier performance of all power levels can be directly affected by either type of degradation and a detailed example is given in the more complex case of "recoverable" characteristics. Class C amplifiers are not directly affected by cumulative ionizing radiation doses of up to 1 Mrad (Si) or emitter-base avalanche although significant transistor hEE degradation can occur in both cases. One example of microwave performance degradation in a Class B/C amplifier is described to illustrate the only known exception to this rule.