A comparison of the GaAs MESFET and the AlGaAs/GaAs heterojunction bipolar transistor for power microwave amplification

The study is normalized by constraining the devices to specific application: 1-W RF output power at 10 GHz. It is shown that the power gain and thermal resistance are higher and input impedances lower for the heterojunction bipolar transistor (HBT). Because of the higher thermal resistance, the operating temperature is significantly higher for the HBT, limiting the CW power output from the device. If the device area is increased to reduce the power density, then the input impedance (common emitter) will be proportionally reduced, making input matching much more difficult.<
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