Constant voltage output circuit
Provided is a constant voltage output circuit having an output terminal and configured to supply power to a crystal oscillator circuit connected to the output terminal, the constant voltage output circuit, having: a bias current control circuit subjected to negative feedback control by an output voltage which is supplied from the output terminal. As a result, variation in the constant voltage output caused by variation in current from a constant current source is reduced.
1. A constant voltage output circuit having an output terminal and configured to supply power to a crystal oscillator circuit connected to the output terminal,
the constant voltage output circuit, comprising:
a constant current circuit;
a bias current control circuit subjected to negative feedback control by an output voltage which is supplied from the output terminal; and
a constant voltage circuit,
the bias current control circuit including a first transistor, a second transistor, and a third transistor,
a drain terminal of the first transistor being supplied with a current determined by the constant current circuit, a control terminal of the first transistor being connected to a control terminal of the second transistor and the output terminal of the constant voltage output circuit, and a source terminal of the first transistor being connected to a drain terminal of the second transistor,
a source terminal of the second transistor being connected to a power supply terminal, and
a drain terminal of the third transistor being connected to the constant voltage circuit, a source terminal of the third transistor being connected to the power supply terminal.
2. A constant voltage output circuit according to claim 1 , further comprising:
a switch configured to stop operation of the constant voltage circuit;
a holding circuit configured to hold the output voltage; and
a control signal generation circuit configured to control the switch.
3. A constant voltage output circuit having an output terminal and configured to supply power to a crystal oscillator circuit connected to the output terminal, the constant voltage output circuit, comprising:
a bias current control circuit subjected to negative feedback control by an output voltage which is supplied from the output terminal;
a constant voltage circuit;
a switch configured to stop operation of the constant voltage circuit;
a holding circuit configured to hold the output voltage; and
a control signal generation circuit configured to control the switch.