Abstract: 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 circuit 3a configured such that transistors M1, M2 are operable to cooperatively supply a given voltage across a resistor RS to generate a stabilized current IR1. In order to vary the output current, the constant current source circuit includes a switching circuit 5 (transistor M5) connected in series to a series circuit connecting in series the transistor M1 and the resistor RS, and a second constant current circuit 4 connected in parallel to a series circuit connecting in series the transistor M1, the resistor RS and the transistor M5.

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.

Abstract: 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 circuit 3a configured such that transistors M1, M2 are operable to cooperatively supply a given voltage across a resistor RS to generate a stabilized current IR1. In order to vary the output current, the constant current source circuit includes a switching circuit 5 (transistor M5) connected in series to a series circuit connecting in series the transistor M1 and the resistor RS, and a second constant current circuit 4 connected in parallel to a series circuit connecting in series the transistor M1, the resistor RS and the transistor M5.

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.