Offset based feedforward amplifier with nonlinearity compensation and P1dB expansion

This paper presents the design of a 6-path offset based feedforward amplifier with high linearity. It leads to both high order nonlinearity compensation and 1dB compression point (P1dB) expansion at the same time. The structure avoids the use of extra gain stages and the superposition mechanism improves the gain which saves the power. The linearized amplifier was implemented by the 130nm SiGe technology. The experimental results was tested under 1.1GHz input frequency, and shows a 3dBm IIP3, >45dBm HP2 and −11dBm P1dB linearity performance with a nontraditional IM3 slope lower than −3dB/dB within the compensation window. A 15dBm compression point expansion and 19dBm nP3 improvement were achieved. The tested voltage gain was 15.5dB with noise figure around 2.9dB under good input matching condition. The core circuits consume 4.8mW from 1.8V power supply and the chip occupies 0.03mm2 area.