Nested-Current-Mirror Rail-to-Rail-Output Single-Stage Amplifier With Enhancements of DC Gain, GBW and Slew Rate Zushu Y an, Student Member , IEEE

Abstract

For better area and power efficiencies, rail-to-rail- output single-stage amplifiers are a potential replacement of their multi-stage counterparts, especially for display applications that entail massive buffer amplifier s in their column drivers. This paper describes a nested-current-mirror (NCM) technique for a single-stage amplifier to achieve substantial enhancements of DC gain, gain-bandwidth product (GBW) and slew rate (SR). Specifically, NCM is customizable for different mirror steps, and sub mirror ratios, to balance the performance metrics and capac- itive-load ( ) drivability, avoiding any compensation passives while preserving a rail-to-rail output swing. Analytical treatments of the NCM technique in terms of performance limits and robust- ness reveal that the NCM amplifier can surpass the fundamental power-efficiency limit set by the basic differential-pair (DP) am- plifier. Two prototypes, 3-step and 4-step NCM amplifiers, were fabricated in 0.18 m CMOS for systematic comparison with the DP amplifier. The former represen ts a robust design exhibiting 72 dB DC gain and 0.0028–0.27 MHz GBW over 0.15–15 nF with 80 phase margin (PM). The latter embodies an aggressive design attaining 84 dB DC gain and 0.013–1.24 MHz GBW over 0.15–15 nF with 62 PM. All amplifiers were sized for the same area (0.0013 mm )a n dp o w e r( 3 . 6W).