AM/PM Nonlinearities in SiGe HBTs

An analysis of AM/PM nonlinear distortion in advanced SiGe HBTs is presented. The results show that an optimum bias point exists in the high-injection collector current density regime as the device nears BV_CEO. At this point, the phase deviation remains close to zero, even as the transistor gain goes into compression. This effect can be further optimized by matching the output of the device to its optimum OIP₃ impedance. These results should prove useful for power amplifier design for high data rate electronic systems, which typically require high peak-to-average power ratios.