US 4,908,566 A · Voltage regulator having staggered pole-zero compensation network

Abstract

The feedback control loop of the common-emitter output transistor stage of a low dropout voltage regulator imcorporates a staggered pole-zero network, which effectively introduces an incremental reduction, or rolloff, in gain, and an accompanying reduction in phase shift with increase in frequency, so that, at the unity gain point of the transfer characteristic, there is still substantial phase margin, thus preventing the circuit from being driven into oscillation. The RC load pole location can vary widely and stability is maintained. The network is configured as a staggered resistor-capacitor network comprised of plural resistor-capacitor circuits coupled in cascade between the output of the feedback error amplifier and the input of a buffer amplifier the output of which drives the base of the output stage transistor in order to offset loading effects of the transistor base on the staggered pole-zero network.

Claims16

Dependent claims

A voltage regulator circuit comprising:

an output amplifier stage having an input terminal to which an unregulated input voltage is coupled, an output terminal from which a regulated output voltage is derived, and a control terminal to which a control voltage is applied;
an error amplifier stage having a first input coupled to said output terminal, a second input coupled to receive a reference voltage, and an output from which an error voltage representative of the difference between said regulated output voltage and said voltage is coupled as said control voltage for said output amplifier stage;
and
means, coupled in a feedback path from said output terminal through said error amplifier stage to said control terminal, for maintaining the open loop phase differential between the first input of said error amplifier stage and the output terminal of said output amplifier stage less than 360.degree. for the entirety of the frequency range over which the gain is equal to or greater than unity.

1 more element

A method of maintaining stable operation of a voltage regulator circuit which comprises an output amplifier stage having an input terminal to which an unregulated input voltage is coupled, an output terminal from which a regulated output voltage is derived for application to an output load, and a control terminal to which a control voltage is applied;

and an error amplifier stage having a first input coupled to said output terminal, a second input coupled to receive a reference voltage, and an output from which an error voltage representative of the difference between said regulated output voltage and said reference voltage is coupled as said control voltage for said output amplifier stage;
said method maintaining stable operation of said regulator circuit over the entirety of the frequency range over which gain is equal to or greater than unity, irrespective of the pole-zero characteristics of the output load, comprising the steps of:
providing a staggered hole-zero compensation network in a feedback path from said output terminal through said error amplifier stage to said control terminal.

A voltage regulator circuit comprising:

an output amplifier stage having an input terminal to which an unregulated input voltage is coupled, an output terminal from which a regulated output voltage is derived for application to an output load, and a control terminal to which a control voltage is applied;
an error amplifier stage having a first input coupled to said output terminal, a second input coupled to receive a reference voltage, and an output from which an error voltage representative of the difference between said regulated output voltage and said reference voltage is coupled as said control voltage for said output amplifier stage;
and
means for maintaining stable operation of said regulator circuit over the entirety of the frequency range over which gain is equal to or greater than unity irrespective of the pole-zero characteristics of the output load, said means comprising a staggered pole-zero compensation network in a feedback path from said output terminal through said error amplifier stage to said control terminal.

1 more element

Dependencies are inferred from the claim text.

Voltage regulator having staggered pole-zero compensation network

Life of this patent

Voltage regulator having staggered pole-zero compensation network

Life of this patent

Abstract

Claims16