Temperature insensitive PA bias circuit with digital control interface using InGaP/GaAs HBT technology

This paper demonstrates a new temperature insensitive bias circuit using a Wilson current mirror for the InGaP/GaAs HBT power amplifier. The Wilson current mirror has a high impedance node for connecting an on/off digital interface and a stable voltage node for injection of feedback signals to achieve a temperature insensitive bias. The fabricated output stage of the power amplifier with the feedback through the Wilson current source shows a stable bias current with current variation from 186 mA to 182 mA for the temperature range from 25 oC to 200 oC. A bias circuit without the feedback through the Wilson current source is also fabricated for comparison and shows a strong bias current variation over temperature.