Record power added efficiency of bipolar power transistors for low voltage wireless applications

To increase the power added efficiency (PAE) of low voltage RF bipolar power transistors for cellular applications, we investigated the influence of transistor parasitics on PAE. We found that reducing the output capacitance increases the PAE due to better second harmonic tuning. By optimizing the transistor for a low output capacitance we achieved a record PAE of 71% at 0.5 Watt, 1.8 GHz and 3.5 V supply voltage.