A new concept of ballasting mechanisms of microwave power transistors in class C operation

Emitter ballasting in class C microwave power transistors is shown to cause a sacrifice of output power and collector efficiency. The use of base impedance balasting resulted in the development of an experimental 4 GHz microwave power transistor which is capable of providing 3 watts of output power with a 6.4 dB power gain and a 65% collector efficiency. The experimental data on the collector current dependence of the power gain, and the spatial temperature distribution of the device working in class C and class A operations are presented. General guidelines for designing class C microwave transistors for optimum performance are given.