High Frequency Unity Gain Buffer in 90-nm CMOS Technology

Abstract

A new unity gain buffer architecture is presented for on-chip CMOS mixed signal applications. The proposed two-stage common source active load (CSAL) buffer with source feedback offers improved performance compared to previously published source follower and source-coupled differential-pair-based unity gain buffers. A 90-nm CMOS design ([Formula: see text] equals 1.2[Formula: see text]V) of the buffer has the following performance parameters. With [Formula: see text]/[Formula: see text] of 10 fF/250 fF, [Formula: see text] is 4.4[Formula: see text]GHz, low frequency gain is 0.16[Formula: see text]dB, maximum input range within 2% gain variation is 260[Formula: see text]mV, total harmonic distortion (THD) is [Formula: see text]63.3[Formula: see text]dB, offset error (input offset minus output offset) is 26[Formula: see text]mV, and 1.06[Formula: see text]mW power consumption. The active load, low gain amplifiers eliminate stability issues and any need for compensation capacitors. The architecture facilitates a relatively large input/output voltage swing while keeping transistors operating in the saturation region, making it suitable for submicron technologies with low rail voltages.