High-Efficiency Balanced Switched-Path Monolithic SiGe HBT Power Amplifiers for Wireless Applications

Modern wireless telecommunication systems require high-efficient, linear, low cost and long talk-time solutions. The proposed novel balanced circuit for power amplifiers provides a high efficiency at maximum as well as backoff output power levels and low sensitivity to load variations. To minimize the quiescent current at low output power levels, an adaptive current-mirror bias circuit can be effectively used. Experimental results for highly efficient, linear, multi-band and multi-mode, two-stage, balanced switched-path SiGe HBT power amplifiers, intended to operate across the DCS 1800, PCS 1900, WCDMA 850/1900/2100 frequency bands, exhibit a peak power-added efficiency of ges50 % at 33 dBm and ges20 % at 16 dBm of output power with a minimum quiescent current of 12 mA.