Abstract
An approach to implement single-ended power-efficient static class-AB Miller op-amps with symmetrical and significantly enhanced slew-rate and accurately controlled output quiescent current is introduced. The proposed op-amp can drive a wide range of resistive and capacitive loads. The output positive and negative currents can be much higher than the total op-amp quiescent current. The enhanced performance is achieved by utilizing a simple low-power auxiliary amplifier with resistive local common-mode feedback that increases the quiescent power dissipation by less than 10%. The proposed class AB op-amp is characterized by significantly enhanced large-signal dynamic, static current efficiency, and small-signal figures of merits. The dynamic current efficiency is 15.6 higher, the static current efficiency is 10.6 times higher, and the small-signal figure of merit is 2.3 times higher than the conventional class-A op-amp. A global figure of merit that determines an op-amp’s ultimate speed is 6.33 times higher than the conventional class A op-amp.
Highlights
In the conventional class-A Miller op-amp with an NMOS input stage [2,3] shown in Figure 1a, the NMOS output transistor limits the peak negative output current to a value IoutQ
Corresponding to the output branch’s quiescent current. This imposes a severe limitation in the op-amp’s negative slew rate (SR− ). This can be expressed as SR− = (IoutQ − IRL )/
The circuit implementation of both VBAT and the control circuit [7,8] can be relatively complex and increases the total op-amp’s quiescent current. This can significantly lower the current efficiency of the class-AB op-amp
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In the conventional class-A Miller op-amp with an NMOS input stage [2,3] shown, the NMOS output transistor limits the peak negative output current to a value IoutQ corresponding to the output branch’s quiescent current This imposes a severe limitation in the op-amp’s negative slew rate (SR− ). The voltage signal model of the class-AB op-amps based on the floating battery [6] scheme is shown in VX drives the output PMOS transistor MOP. The circuit implementation of both VBAT and the control circuit [7,8] can be relatively complex (as shown in Figure 2b and in the circuit of [8]) and increases the total op-amp’s quiescent current This can significantly lower the current efficiency of the class-AB op-amp.
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