Toko, Inc.

Satoru Yamane

Hiroshi Tanigawa

Shuichi Nakamura

Disclosed is a variable output-type constant current source circuit capable of varying its output current in a stepwise manner without the complication in circuit configuration and the increase in size of a semiconductor circuit board for incorporating the circuit therein. The constant current source circuit comprises a first self-biasing type constant current circuitconfigured such that transistors M, Mare operable to cooperatively supply a given voltage across a resistor RS to generate a stabilized current I. In order to vary the output current, the constant current source circuit includes a switching circuit(transistor M) connected in series to a series circuit connecting in series the transistor Mand the resistor RS, and a second constant current circuitconnected in parallel to a series circuit connecting in series the transistor M, the resistor RS and the transistor M. The second constant current circuitis also configured to serve as an activation circuit for the first constant current circuit

Variable output-type constant current source circuit

Disclosed is a constant voltage power supply, which comprises an error amplifier VEA including a transistor Mand a transistor Mhaving the same ratio between channel width and channel length as that of the transistor MThe gate and source of the transistor Mare connected to the gate of a transistor Mto form a current mirror circuit in conjunction with the transistor MFurther, the drain of the transistor Mis connected with a transistor Madapted to be switched in response to an external control signal Sg. For example, when the transistor Mis in ON state, any signal amplification function of the transistor Mis 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.

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Tsurugashima, Japan

Satoru Yamane