US 2004/0104712 A1Published application

Constant voltage power supply

AssigneeToko, Inc.

InventorsHiroshi Tanigawa, Satoru Yamane

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Abstract

Disclosed is a constant voltage power supply, which comprises an error amplifier VEA including a transistor M3, and a transistor M4 having the same ratio between channel width and channel length as that of the transistor M3. The gate and source of the transistor M4 are connected to the gate of a transistor M3 to form a current mirror circuit in conjunction with the transistor M3. Further, the drain of the transistor M4 is connected with a transistor M5 adapted to be switched in response to an external control signal Sg. For example, when the transistor M5 is in ON state, any signal amplification function of the transistor M3 is vanished away, and the gain of the error amplifier VEA is lowered. The circuit configuration for changing the gain of the error amplifier VEA makes it possible to strike a balance between high-speed response characteristic in an active mode and operational stability in a sleep mode, and reduce a circuit area required for being formed on an integrated circuit.

Claims4

Dependent claims

A constant voltage power supply including a series control transistor connected between of input and output terminals of said constant voltage power supply, and an error amplifier circuit having an output terminal connected to a control terminal of said series control transistor, wherein the operation of said series control transistor is controlled in accordance with an output voltage signal supplied to one input terminal of said error amplifier circuit from said series control transistor, and a reference voltage signal supplied to another input terminal of said error amplifier circuit, so as to provide an stabilized output voltage, said constant voltage power supply comprising:

a first amplifier circuit including first and second transistors, wherein one ends of the respective main current paths of said first and second transistors are connected to a common node to allow said first and second transistors to be formed as a differential pair;
a second amplifier circuit including a third transistor which has an control terminal adapted to be supplied with a signal appearing at the other end of the main current path of said second transistor;
a fourth transistor having an control terminal and an main current path, wherein said control terminal and one end of said main current path are connected to said control terminal of said third transistor to provide a current mirror circuit in conjunction with said third transistor;
and
a first switch connected in series to the other end of the main current path of said fourth transistor and adapted to be switched in response to an external control signal.

2 more elements

Dependencies are inferred from the claim text.