AC stabilization using a low frequency zero created by a small i

Details AC stabilization using a low frequency zero created by a small i AC stabilization using a low frequency zero created by a small i

1991-06-14

1992-12-01

Voeltz, Emanuel T.

Electricity: power supply or regulation systems

Self-regulating

Using a three or more terminal semiconductive device as the...

323314, 323315, 323907, 307491, 307591, G05F 330

Patent

active

051682095

ABSTRACT:
AC stabilization and temperature compensation improves phase margin and permits high temperature (significantly above 125.degree. C.) operation for an exemplary low drop-out voltage regulator with a PNP output transistor. The low drop-out voltage regulator (FIG. 1) includes a PNP output transistor (Q.sub.OUT) together with a voltage reference circuit (12), a gain circuit (14), and a current limit circuit (16). To provide AC stabilization, a small internal capacitor (C.sub.INT) of about 10 pF is coupled between the input of the gain circuit and the base of the output PNP, using Miller multiplication to substantially increase the effective capacitance of the stabilization capacitor, and introducing a zero into the gain-phase plot for the voltage regulator, substantially cancelling the pole, with a concomitant increase in phase margin. To provide temperature compensation, a dual-collector temperature compensation PNP (Q.sub.TC) is configured as a current mirror current source that, at high temperatures with collector currents less than uncompensated or resistively compensated junction leakage currents, the temperature compensation PNP provides the required negative base drive to supply sufficient hole current into the base of the output PNP to offset junction leakage.

REFERENCES:
patent: 4500831 (1985-02-01), Akram
patent: 4908566 (1990-03-01), Tesch
patent: 5023567 (1991-06-01), O'Shaughnessy et al.
patent: 5029295 (1991-07-01), Bennett et al.

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