Using auxiliary amplifier to cancel third-order intermodulation distortion for a 1.9 GHz CMOS linear amplifier design

A new linearization method for microwave amplifier design, by canceling the third-order intermodulation component, is proposed. The main amplifier is combined with an auxiliary amplifier, whose gain and bias conditions are appropriately designed. The output frequency spectra of the main amplifier are subtracted by this auxiliary amplifier. The third-order distortion is canceled since these two amplifiers are designed as a differential-pair stage. IIP/sub 3/ improvement as large as 11 dB has been obtained, where this amplifier achieves a 11.5 dB gain at 1.9 GHz, and is fabricated using 0.18 /spl mu/m CMOS technologies. The circuit consumed 11.5 mA or 11 mA for the auxiliary amplifier on or off, respectively. The auxiliary amplifier consumes less than 0.8 mW DC power and causes only 0.2 dB gain reduction of the main amplifier.