Architecture considerations of LTE/WCDMA wideband power amplifier for efficiency improvement

An enhanced architecture for a broadband power amplifier (PA) for LIE and WCDMA handsets using InGaP/GaAs hetero-junction bipolar transistor (HBT) process is presented. A two-stage PA solution adopting switchable driver-stage amplifier without employing input switch is proposed to reduce loss and help with power efficiency improvement. Furthermore, in order to enhance the power-added efficiency (PAE) at the low output power level, a two-chain amplifying structure in parallel has been implemented. For wideband 1.71-1.98GHz, the fabricated PA shows >27dB of Gain and >38% of PAE with <80mA of quiescent current (I-cq) at the output power (Pout) of 28dBm for high-power mode operation, as well as >16dB of Gain and >13% of PAE with <20mA of I-cq at the Pout of 17dBm for low-power mode operation. The system power usage efficiency are obviously enhanced with the presented two-stage dual-chain PA architecture.