Constant voltage outputting circuit
View Patent ↗A constant voltage outputting circuit has a differential amplification circuit having two inputs and an output that is connected to a gate of an output transistor. The output transistor is connected between a power supply voltage and an output terminal and controls an output voltage at the output terminal based on an output of the differential amplification circuit. A voltage division resistor divides the output voltage and applies a divided voltage to one input of the differential amplification circuit, and a reference voltage is applied to the other input thereof. A capacitor connected between the power supply voltage and the gate of the output transistor stabilizes the output voltage when the power supply voltage changes.
1. A constant voltage outputting circuit, comprising:
a voltage division resistor that divides an output voltage at an output terminal and provides a divided voltage;
a reference voltage circuit that outputs a reference voltage;
a differential amplification circuit having one input terminal that receives the divided voltage and another input terminal that receives the reference voltage.
an output transistor connected between a power supply voltage and the output terminal for controlling the output voltage at the output terminal based on an output of the differential amplification circuit;
a capacitor connected between the power supply voltage and a gate terminal of the output transistor;
another transistor having a gate terminal connected to an output terminal of the differential amplification circuit; and
a constant current circuit connected to a source-drain path of the other transistor, the gate terminal of the output transistor being connected to a node between the source-drain path and the constant current circuit.
2. A constant voltage outputting circuit according to claim 1 ; wherein each of the output transistor and the other transistor is a PMOS transistor.
3. A constant voltage outputting circuit according to claim 2 ; wherein the constant current circuit includes a PMOS depletion type transistor.