Bias optimized IP2 & IP3 linearity and NF of a decade-bandwidth GaN MMIC feedback amplifier

This paper describes the bias-optimized performance of a 0.25-3.5GHz Cascode feedback amplifier which achieves flat-gain over a decade of BW. The LNA is fabricated using 0.25um GaN HEMT technology with fT ~ 50 GHz and BVgd >; 60V. A Cascode device is used for enhanced electrical and thermal performance but requires bias optimization. At an optimum low-noise bias of 10V-200mA, a remarkable NF of 0.88dB with P1dB >; 1Watt and OIP3 of 38.7dBm is obtained at 2 GHz. This is believed to be the lowest NF achieved from a multi-octave BW flat-gain GaN LNA with greater than 1-Watt P1dB. At maximum IP2 and IP3 bias of 40V-500mA, the LNA achieves 20dB of flat-gain over a 250-2500MHz decade-band and a 3-dB BW of ~ 3.5 GHz. An IP3 of 50.6 dBm, a high IP2 of 70.5 dBm, and a P1B of 37.5 dBm (5.6-Watts) is achieved at 2 GHz with a corresponding NF of 2.2dB. This is an improvement in NF for state-of-the-art GaN LNAs with IP3 >; 50 dBm and flat decade-BW gain response. Additional GaN bias-performance combinations are also revealed which indicate promise for next generation CATV, FTTX, software defined radio and BTS applications.