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Frequency compensation techniques for multiple-stage amplifiers are becoming increasingly important as cascode configuration is not applicable to low-voltage design. Nested Miller compensation (NMC) is commonly used to stabilize multiple-stage amplifiers. However, the bandwidth of an NMC amplifier is poor. Several topologies such as multi-path nested Miller compensation (MNMC) and nested Gm-C compensation (NGCC) have been proposed to enhance the bandwidth. When compared to an NMC amplifier, MNMC can increase the bandwidth by approximately a factor of two while NGCC can further improve the stability of the amplifier. Nevertheless, the bandwidth enhancement by the two topologies is not sufficient for high-speed applications especially to drive large capacitive loads, such as the error amplifier in a low-voltage low-dropout regulator in portable electronic devices. A topology called damping-factor-control frequency compensation (DFCFC) for three-stage amplifiers significantly increases the bandwidth and improves the transient response of the amplifiers.
Date of Conference: 17-17 Feb. 1999