Low dropout voltage regulator with quiescent current reduction
First Claim
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1. A voltage regulator circuit having an input terminal, a ground and an output terminal, said circuit comprising:
- a pass transistor having emitter, base and collector electrodes with the emitter coupled to the input terminal and the collector coupled to the output terminal;
a first switch for coupling the pass transistor base to the output terminal;
a second switch for coupling the pass transistor base to ground; and
a differential amplifier having a first input coupled to said input terminal, a second input coupled to said output terminal and an output coupled to said first and second switches whereby said differential amplifier operates to activate said first and second switches as a function of the regulator input-output voltage differential.
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Abstract
A low dropout voltage regulator with quiescent current reduction has a pass transistor coupled for conduction from a positive supply terminal to a regulated output terminal. A first switch is coupled to conduct the base current of the pass transistor to the regulated output terminal. A second switch is coupled to conduct the base current of the pass transistor to ground. A control circuit selects the action of the switches to select the conduction path for base current.
42 Citations
17 Claims
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1. A voltage regulator circuit having an input terminal, a ground and an output terminal, said circuit comprising:
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a pass transistor having emitter, base and collector electrodes with the emitter coupled to the input terminal and the collector coupled to the output terminal; a first switch for coupling the pass transistor base to the output terminal; a second switch for coupling the pass transistor base to ground; and a differential amplifier having a first input coupled to said input terminal, a second input coupled to said output terminal and an output coupled to said first and second switches whereby said differential amplifier operates to activate said first and second switches as a function of the regulator input-output voltage differential. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A low dropout voltage regulator with quiescent current reduction having positive and negative supply terminals for connection to a source of operating voltage, and having a regulated output terminal, comprising:
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a pass transistor with emitter, base, and collector, with emitter coupled to said positive supply terminal and collector coupled to said regulated output terminal; a first driver coupling said pass transistor base to said regulated output terminal; a second driver coupling said pass transistor base to said negative supply terminal; an emitter coupled differential amplifier with first and second inputs, and complementary first and second outputs, with complementary first and second outputs connected to activate respectively said first and second drivers. a first voltage source connected to said differential amplifier first input; a second voltage source connected to said differential amplifier second input; an error amplifier with first and second inputs and an output, with first input coupled to said regulated output terminal, with second input coupled to a voltage reference, and with output coupled to control the emitter current flowing in said emitter coupled differential amplifier. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A low dropout voltage regulator with quiescent current reduction having positive and negative supply terminals for connection to a source of operating voltage, and having a regulated output terminal, comprising:
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a PNP pass transistor with emitter coupled to said positive supply terminal, and collector coupled to said regulated output terminal; a first PNP driver transistor with emitter coupled to said pass transistor base, and with collector coupled to said regulated output terminal; a second PNP driver transistor with emitter coupled to said pass transistor base, and with collector coupled to said negative supply terminal; a first NPN transistor of an emitter coupled differential pair with base coupled to a first voltage reference connected to follow the voltage of the positive supply terminal, and collector coupled to said first driver transistor base; a second NPN transistor of the emitter coupled differential pair with base coupled to a second voltage reference connected to follow the voltage of the regulated output terminal, and collector coupled to said second driver transistor base;
an error amplifier with inverting and non-inverting inputs, and an output, with said inverting input coupled to said regulated output terminal, and with said non-inverting input coupled to a third voltage reference, and with said output coupled to emitters of said first and second transistors of an emitter coupled differential pair. - View Dependent Claims (14, 17)
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15. A method of operating a voltage regulator between an input terminal and ground, with an output terminal, comprising the steps of:
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creating a conducting path between the input terminal and output terminal by a pass transistor; conducting said pass transistor base current through a driver transistor to the output terminal; connecting inputs of a differential amplifier between the input terminal and the output terminal for detecting a reduced voltage differential from said input terminal to said output terminal; and conducting said pass transistor base current to ground as a result of said detecting step.
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16. A method of operating a low dropout voltage regulator with quiescent current reduction between poaitive and negative supply terminals, with a regulated output terminal comprising the steps of:
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creating a conducting path from the positive supply terminal to the regulated output terminal by a pass transistor; controlling base current of the pass transistor by a driver transistor; activating a first path for said base current of the pass transistor to the regulated output terminal; coupling inputs of a differential amplifier between the positive supply terminal and the regulated output terminal for detecting a reduced difference of positive supply terminal to regulated output terminal voltage; and activating a second path for said base current of the pass transistor to the negative supply terminal as a result of the detecting step.
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Specification