High Linearity Dynamic Feedback Darlington Amplifier

This paper reports on a novel InGaP HBT Darlington RF amplifier which employs dynamic feedback linearization in order to improve IP3 and P1dB compression. The dynamic feedback amplifier obtains 20 dB gain, a 0.05-4 GHz BW, a P1dB and IP3 of 21.2 dBm and 40 dBm, respectively at 2 GHz. Compared to a conventional Darlington feedback design using equivalent quiescent bias of 5V-30mA, the dynamic feedback Darlington achieved an improvement of 7.5 dB in P1dB and 11 dB in IP3. A record IP3/Pdc ratio linearity figure of merit (LFOM) of 55.4:1 and 26.9:1 were obtained at 850 MHz and 1.95 GHz. These results are believed to be the best IP3 LFOM results reported for a 5V wide band Darlington feedback amplifier.