Abstract
A highly power-efficient, fully differential Miller op-amp with accurately controlled output quiescent current is introduced. The op-amp can drive both capacitive and resistive load due to the presence of the auxiliary amplifier. This amplifier helps to achieve class AB operation of the proposed op-amp. The fully differential auxiliary amplifier is compact and uses a resistive local common-mode feedback network. It consumes only 6% of the total current of the op-amp. The proposed op-amp has several innovative features. Incorporating the auxiliary amplifier helps to improve the unity gain frequency, power efficiency, slew-rate, and common-mode rejection ratio of the proposed op-amp. It can drive a wide range of resistive (200 Ω–1 MΩ) and capacitive loads (5 pF–300 pF). The op-amp has a large signal dynamic current efficiency of 8.6 and a large signal static current efficiency of 7.9. The small-signal figure of merit is 8.7 for RL = 1 MΩ and 7.3 for RL = 200 Ω.
Highlights
Differential signal processing is a wise choice to maintain signal integrity in highspeed data acquisition systems such as communications, imaging, instrumentation, and video applications
The proposed class-AB op-amp shown in Figure 1 is a fully differential operational amplifier that can drive a wide range of resistive and capacitive loads
The proposed and conventional class-A (Conv-A) op-amps are simulated with Cadence using TSMC 180 nm CMOS technology parameters
Summary
Differential signal processing is a wise choice to maintain signal integrity in highspeed data acquisition systems such as communications, imaging, instrumentation, and video applications. Analog-to-digital converters [1] are essential components in high-speed data acquisition systems [2] They need a differential amplifier to drive their differential input. Designing a power-efficient fully differential amplifier [6] that can drive a wide range of resistive and capacitive loads is very useful for today’s batteryoperated portable electronic equipment, e.g., for the Internet of Things (IoT) [7] applications. In order to maintain a well-defined constant output quiescent current, IoutQ independent on supply voltage, nominal component values, and technology parameter variations, the floating battery scheme requires an additional IoutQ control circuit. An improved class-AB op-amp is implemented by utilizing a compact fully differential auxiliary amplifier instead of two floating batteries.
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