Abstract

This paper describes a differential operational amplifier designed for high speed applications. The amplifier consists of a folded cascode amplifier first stage, and a class A output stage for additional gain. The amplifier is compensated with cascoded Miller compensation described in [1] and uses the bias circuitry described in [2]. The worst case amplifier dissipates 3.26mW, settles to 0.1% in 14nS (C L ~ 1.5pF), occupies 3491m 2 , has a gain of 55K, and operates on a 2.5V power supply. 2.0 AMPLIFIER ARCHITECTURE 2.1 Differential Amplifier FIGURE 1. Differential-mode amplifier schematic (excluding bias circuits and CMFB) Figure1 shows the differential-mode amplifier schematic excluding bias circuits and common -mode feedback amplifier. A class A output stage was chosen for maximum output swing under low supply operation. With a shifted input common-mode voltage the minimum supply voltage and thus the desired output range is limited primarily by the first casV

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