Operational amplifier
An operational amplifier includes an input stage amplifier that receives an input signal, an output stage amplifier that amplifies a signal output from the input stage amplifier and outputs the signal, a capacitor that is connected between an input node and an output node of the output stage amplifier, and a charge and discharge control circuit that controls a charge and discharge current of the capacitor.
1 . An operational amplifier comprising:
an input stage amplifier that receives an input signal;
an output stage amplifier that amplifies a signal output from the input stage amplifier and outputs the signal;
a capacitor that is connected between an input node and an output node of the output stage amplifier; and
a charge and discharge control circuit that controls a charge and discharge current of the capacitor.
2 . The operational amplifier according to claim 1 , wherein
the charge and discharge control circuit includes a first switch having a common terminal connected to one end of the capacitor, a break terminal connected to the output node of the output stage amplifier and a make terminal connected to a first power supply, and a second switch having a first terminal connected to the other end of the capacitor and a second terminal connected to a second power supply, and
in state transition mode when an output voltage of the output stage amplifier makes transition, the common terminal and the make terminal of the first switch have continuity, and the first terminal and the second terminal of the second switch have continuity.
3 . The operational amplifier according to claim 2 , wherein
the first power supply is a circuit that is connected in a previous stage of the input stage amplifier and outputs the input signal.
4 . The operational amplifier according to claim 2 , wherein
the first power supply is a first voltage source that outputs a prescribed voltage value.
5 . The operational amplifier according to claim 2 , wherein
the second power supply is a power supply that supplies an operating power to at least one of the input stage amplifier and the output stage amplifier.
6 . The operational amplifier according to claim 2 , wherein
the second power supply is a second voltage source that generates voltages having a prescribed voltage difference from a voltage of a power supply that supplies an operating power to at least one of the input stage amplifier and the output stage amplifier.
7 . The operational amplifier according to claim 1 , wherein
the input stage amplifier is a differential amplifier, and an inverting input terminal of the input stage amplifier is connected to the output node of the output stage amplifier.
8 . The operational amplifier according to claim 1 , wherein
the input stage amplifier is a differential amplifier, and an inverting input terminal of the input stage amplifier is connected to a terminal of the capacitor on a side of the output node of the output stage amplifier.
9 . The operational amplifier according to claim 1 , wherein
the first switch and the second switch change continuity according to a control signal.
10 . The operational amplifier according to claim 9 , wherein
the control signal is a strobe signal that is used in a liquid crystal display device.
11 . The operational amplifier according to claim 1 , wherein
a third switch is connected between the output node of the output stage amplifier and an output terminal and changes continuity between the output node and the output terminal.
12 . The operational amplifier according to claim 1 , wherein
the input stage amplifier outputs a first signal and a second signal in-phase with each other, the output stage amplifier includes a first input node to receive the first signal and a second input node to receive the second signal, a first capacitor is connected between the first input node and the output node, and a second capacitor is connected between the second input node and the output node,
the charge and discharge control circuit includes a first switch having a common terminal connected to one ends of the first capacitor and the second capacitor, a break terminal connected to the output node of the output stage amplifier and a make terminal connected to a first power supply, a second switch having a first terminal connected to the other end of the first capacitor and a second terminal connected to a positive power supply, and a third switch having a first terminal connected to the other end of the second capacitor and a second terminal connected to a negative power supply, and
in state transition mode when an output voltage of the output stage amplifier makes transition, the common terminal and the make terminal of the first switch have continuity, the first terminal of the second switch and the second terminal of the second switch have continuity, the first terminal of the third switch and the second terminal of the third switch have continuity, and the output node of the output stage amplifier becomes high impedance.
13 . The operational amplifier according to claim 12 , wherein
the positive power supply and the negative power supply are power supplies that supply an operating power to at least one of the input stage amplifier and the output stage amplifier.
14 . The operational amplifier according to claim 12 , wherein
the positive power supply and the negative power supply are a second voltage source and a third voltage source, respectively, that generate voltages having a prescribed voltage difference from voltages of power supplies that supply an operating power to at least one of the input stage amplifier and the output stage amplifier.
15 . The operational amplifier according to claim 12 , wherein
the first switch, the second switch and the third switch change continuity according to a control signal.
16 . The operational amplifier according to claim 15 , wherein
the control signal is a strobe signal that is used in a liquid crystal display device.
17 . The operational amplifier according to claim 1 , wherein
the operational amplifier is a source driver in a liquid crystal display device.