Adaptive LDMOSFET Drain and Dummy-Gate Biases for Highly Modulated Signals

Abstract

Adaptive biases are proposed for both the drain and the dummy gate of LDMOSFETs to improve their overall efficiency in amplification of highly modulated signals. At low input power, the drain bias is reduced to maintain high efficiency. At high input power, the dummy-gate bias is increased to maintain high linearity. By using such adaptive biases on both the drain and dummy gate, the measured efficiency on an LDMOSFET for a signal with a 9-dB peak-to-average modulation ratio is 16 percentage units higher than that with fixed biases and 5 percentage units higher than that with adaptive bias on the drain alone.