Power Amplifier with Temperature Adaptive Biasing for improved DEVM

This paper describes DEVM challenges and long packet issues during a linear Power Amplifier (PA) design. Based on Hetero-junction Bipolar Transistor (HBT) electrothermal behavior, a programmable temperature compensating bias is designed to improve the PA linearity. This temperature compensation is applied to a fully integrated 5 GHz BiCMOS HBT PA to improve the DEVM over a junction temperature range from 25°C to 180°C. For a long packet data transmission (4 ms), the power gain variation is reduced to only 156 mdB for an 8μs preamble and 27 mdB for a 90μs preamble. With the proposed temperature adaptative bias, the PA can achieve DEVM lower than -47 dB up to 16.5 dBm output power.