Temperature effect on power characteristics of SiGe HBTs

In this paper, the linear power gain, gain expansion and gain compression of power SiGe HBTs at various temperatures have been presented. At low base voltage, the linear power gain increases with increasing temperature, while the linear power gain decreases at high base voltage. Besides we observe the gain expansion will exist as base voltage is in low value, but it will disappear when the temperature increases to 75°C. After gain compression, the power gain increases with increasing temperature no matter what the base voltage is. We explain this phenomenon by analyzing the cutoff frequency and the collector current at different temperatures.