Nested-Current-Mirror Rail-to-Rail-Output Single-Stage Amplifier With Enhancements of DC Gain, GBW and Slew Rate

Abstract

For better area and power efficiencies, rail-to-railoutput single-stage amplifiers are a potential replacement of their multi-stage counterparts, especially for display applications that entail massive buffer amplifiers 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 capacitive-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 robustness reveal that the NCM amplifier can surpass the fundamental power-efficiency limit set by the basic differential-pair (DP) amplifier. 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 represents 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 ) and power (3.6 W).Index Terms-Area efficiency, CMOS, current mirror, DC gain, differential-pair (DP) amplifier, frequency compensation, gain-bandwidth product (GBW), low temperature polysilicon LCD, multi-stage amplifier, nested current mirror, rail-to-rail output swing, single-stage amplifier, slew rate (SR), stability.

Enhanced active‐feedback frequency compensation with on‐chip‐capacitor reduction feature for amplifiers with large capacitive load

“…In order to elicit the merits of the AFFC achieved by the proposed compensation topology, a comparison is conducted. Moreover, some typical figure of merits are included in the comparison [3][4][5][6][7]9,[17][18][19][20][21][22]. Because of the varied IC technologies deployed and also the different capacitive load conditions, it is difficult to make direct comparison among the designs discussed.…”

“…Larger values of these figure of merits shall imply a compensation topology that successfully aided the amplifier to attain faster operation, lower power consumption, and more effective use of on-chip compensation capacitance. Moreover, some typical figure of merits are included in the comparison [3][4][5][6][7]9,[17][18][19][20][21][22].…”

Performance Analysis and Design Optimization of Parallel-Type Slew-Rate Enhancers for Switched-Capacitor Applications

“…Generally, all the topologies falling in this category aim to achieve class-AB action on the output branches maintaining the simplicity of the differential pair in the input section. This can be implemented through: (i) non-linear current mirrors [13][14][15][16][17], (ii) transconductor nesting [18,19] or (iii) current recycling [20][21][22][23][24][25][26][27][28][29]. The important feature of such implementations is that the increased output current capability does not involve an increased dc supply power, in contrast with what happens with a static current amplification approach.…”

Survey on Single Stage Amplifiers for Column Drivers in Active Matrix LCD Panels Leading to a Highly Linear Rail-to-Rail Robust Amplifier

“…In state of the art AMLCD, channel buffers must be capable of deriving a wide range of capacitive loads while still maintaining a phase margin ≥60 • , high DC gain (≥66 dB for 10 bit resolution), rail-to rail output swing in order to accomplish higher gray levels as well as a low power consumption [22]. Naturally, several techniques have been presented over the years to improve the downfalls of a conventional single stage amplifier, some of which include current shunting from the differential input stage [23]- [25] and splitting the differential pair into N -sub pairs [22].…”

“…This review leads to the development of a highly linear rail-to-rail robust single stage amplifier which is presented in this paper. The new amplifier is achieved by applying current splitting technique [22] on a rail-torail differential pair [27]. The paper illustrates that the new amplifier is capable of achieving the requirements of display application when configured as a buffer and thus replace conventional multistage amplifiers.…”