UNCONDITIONALLY THERMALLY STABLE CASCODE GAAS HBTS FOR MICROWAVE APPLICATIONS

This letter describes the performance of a thermally stabilized cascod e-heterojuction bipolar transistor (TSC-HBT) that exhibits uncondition al thermal stability without the use of ballast resistors. A thermal i solation inserted between the current source (CE stage) and the power stage (CB stage) eliminates the positive electrothermal feedback that causes thermal runaway in bipolar transistors, The TSC-HBT cell design s with f(max) values in excess of 100 GHz demonstrated about 300% impr ovement in de power dissipation capability compared to conventional ca scode HBT's in a direct comparison.