High speed dynamic bias switching power amplifier for OFDM applications

An efficiency-enhanced power-amplifier system using dynamic bias switching method is presented. The presented system generates two different voltage sources from one source for drain bias of a RF power amplifier. The drain of the RF power amplifier is biased at low voltage level while the input RF signal is detected to be small. The drain bias is rapidly changed to high voltage level when the input RF signal reaches a certain threshold level. The measured drain bias at VH state is 4.6 V with the efficiency of the bias switching system, 49% and at VL is 2.94 V with 86%. The measured result shows that the overall efficiency of the proposed RF power amplifier is improved by 62% compared to that of the fixed bias amplifier, when OFDM signal with bandwidth 8.46 MHz is applied.