Abstract: Temperature characteristics of SiGe HBT are studied.Experiment data show that the variation of VBE with temperature of SiGe HBT is smaller than that of homo-junction silicon BJT.The needed emitter ballast resistance in SiGe HBT is thus smaller than that in Si BJT when thermal stability of transistors is improved.At the same time,the negative differential resistance characteristics of SiGe HBT is also observed at a high collector-emitter voltage and high current,which can prevent the thermal instability of power transistors effectively,and this is not the case with Si devices.Therefore,SiGe HBT is proved to be more suitable for microwave power devices.

Key words: SiGe HBT, temperature characteristics, microwave power transistor