Use of self bias to improve power saturation and intermodulation distortion in CW class B HBT operation

It is shown that a DC base bias circuit can be used to control the RF performance of a heterojunction bipolar transistor (HBT) operating under CW conditions near class B mode. By a careful choice of base bias resistance, gain can be linearized, output power at 1-dB gain compression increased, and intermodulation distortion reduced. Measurements performed on HBTs biased near class B operation showed a 10-dB improvement in 1-dB gain compression point and a 10-dB reduction in intermodulation distortion for moderate power levels. Results for various values of DC base resistance for a typical HBT are presented.<
>