Parasitic Capacitance Optimization of GaAs HBT Class E Power Amplifier for High Efficiency CDMA EER Transmitter

A class E power amplifier (PA) for a CDMA EER transmitter is implemented with GaAs HBT technology. This paper demonstrates an efficiency improvement with a parasitic capacitance compensation circuit. In order to obtain high output power, the PA needs the large emitter size of a main transistor. The larger the emitter size, the higher the parasitic capacitance should be. In particular, the parasitic C_BE affects a distortion of the input voltage signal and decreases the PA´s efficiency. Using the compensation circuit, we obtain 7% collector efficiency improvement at a similar output power level. This PA exhibits output power of 29 dBm and collector efficiency of 71% at 1.9 GHz.