2018 Volume 15 Issue 8 Pages 20180298
A pre-distortion linearized Darlington cascode power amplifier cell is explored for broadband amplifier implementation, with additional inclusion of a RLC peaking network at the base terminal of the cascode transistor, and a RC feedback network at the input Darlington transistor. The RLC peaking network optimizes bandwidth and large signal power gain. The RC feedback network simplifies the design of broadband matching for the input Darlington pair. Most importantly, an optimization method of the input Darlington transistor biased at saturation mode is proposed to function as a predistortion linearizer, which can compensate for gain compression and phase deviation effects of the following cascode power stage. With this compensation technique, the proposed broadband PA operating over a frequency range from 0.2 to 6 GHz achieves higher OIP3 than the conventional Darlington cascode amplifier, resulting in a 5 dB improvement of OIP3 at 6 GHz. A P1 dB ranging from 24 to 27 dBm over the frequency range is achieved by this broadband power amplifier with a 0.27 mm2 InGaP/GaAs HBT chip die.