Effects of temperature on the IMD sweet spots in an LDMOSFET RF power amplifier

This paper reports effects of temperature on the intermodulation distortion (IMD) sweet spots in an LDMOSFET RF power amplifier. The IMD sweet spots, which are affected by not only the variation of input power levels and gate bias voltage but also internal and external temperature variations, are predicted with the simple mathematical approach. The measured IMD sweet spots are well-matched with the predicted results and the optimum gate bias voltages making the IMD sweet spots are changed by different temperatures. It is also known that the IMD sweet spots are mostly related to the quiescent drain current of the power amplifier. For the experiments, a class AB LDMOSFET RF power amplifier is designed and implemented at a band of 2.14 GHz.