Creating Additional Phase Margin In The Open Loop Gain Of A Negative Feedback Amplifier System Using A Boost Zero Compensating Resistor

摘要

A low-dropout voltage (LDO) regulator that creates a zero in the open loop gain using a relatively small-sized current control element to divert part of the supplied load current through a “zero” resistor before adding it to the output load. The main part of the output load is passed through a relatively large second current control element. A control signal generated by an error amplifier (e.g., an op-amp) is used to control the small current control element, but is passed through a boost zero compensating resistor before being applied to the large current control element. The voltage signal developed across the “zero” resistor mimics the magnitude and phase of a zero in the loop. This voltage signal is added to the loop gain by, for instance, using a bypass capacitor, and the resulting feedback signal is supplied to the error amplifier.