Abstract
A simple technique to implement highly power efficient class AB–AB Miller op-amps is presented in this paper. It uses a composite input stage with resistive local common mode feedback that provides class AB operation to the input stage and essentially enhances the op-amp’s effective transconductance gain, the dc open-loop gain, the gain-bandwidth product, and slew rate with just moderate increase in power dissipation. The experimental results of op-amps in strong inversion and subthreshold fabricated in a 130-nm standard CMOS technology validate the proposed approach. The op-amp has $9~\text {V} \cdot \text {pF}/\mu \text {s}\cdot \mu \text{W}$ large-signal figure of merit (FOM) and $17~\text {MHz}\cdot \text {pF}/\mu \text{W}$ small-signal FOM with 1.2-V supply voltage. In subthreshold, the op-amp has $10~\text {V}\cdot \text {pF}/\mu \text {s}\cdot \mu \text{W}$ large-signal FOM and $92~\text {MHz}\cdot \text {pF}/\mu \text{W}$ small-signal FOM with 0.5-V supply voltage.
Highlights
T HE increasing demand for battery-operated portable electronics equipment requires power-efficient analog circuits
The parameters gm and r0 are considered equal here for all unit size transistors. It provides a moderate gain bandwidth product (GBW).The GBW of the class A op-amp of Fig. 1 can be obtained from its dc open-loop gain and the dominant pole at node X is given by the following equation: fPDOM = 1/(2π RX CX )
The Proposed-AB–AB and conventional op-amps were designed in 130-nm CMOS technology with nMOS and pMOS
Summary
T HE increasing demand for battery-operated portable electronics equipment requires power-efficient analog circuits. A simple design approach of a Miller op-amp is presented to enhance gain-bandwidth product (GBW) by a large factor (63 times in the circuit presented here) and the dc open-loop gain by about one order of magnitude with just moderate increase (∼factor 2) in static power dissipation with respect to the conventional op-amp of Fig. 1. This is the author's version of an article that has been published in this journal.
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