US 2020/0052655 A1Published application

Operational amplifier and control method thereof

AssigneeShenzhen Goodix Technology Co., Ltd.

InventorsWEN-CHI WANG, SI HERNG NG

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Abstract

An operational amplifier includes: a first amplifier stage, configured to generate first output voltages according to first input voltages; a second amplifier stage, configured to generate second output voltages according to the first output voltages; a second output stage circuit, configured to replicate an equivalent or a scaled-down version of the first output stage circuit; a first common-mode feedback circuit, configured to keep an output common-mode voltage of the second output stage circuit at a predetermined value; a logic loop circuit configured to, when the operational amplifier operates in a direct current calibration phase, adjust a difference between the first output voltages; a bias circuit, configured to generate a voltage close to a common mode voltage of the first output voltages produced after the operational amplifier is turned on, the voltage serving as a reference voltage of a second common-mode feedback circuit.

Claims20

Dependent claims

An operational amplifier, comprising:

a first amplifier stage, configured to generate a plurality of first output voltages according to a plurality of first input voltages;
a second amplifier stage, coupled to the first amplifier stage, the second amplifier stage configured to generate a plurality of second output voltages according to the first output voltages;
a second output stage circuit, coupled to the second amplifier stage and a first output stage circuit, the second output stage circuit configured to replicate an equivalent or a scaled-down version of the first output stage circuit;
a first common-mode feedback circuit, coupled to the second amplifier stage and the second output stage circuit, the first common-mode feedback circuit configured to keep an output common-mode voltage of the second output stage circuit at a predetermined value;
a logic loop circuit, coupled to the first amplifier stage, the logic loop circuit configured to adjust a difference between the first output voltages of the first amplifier stage;
a bias circuit, configured to generate a voltage close to a common-mode voltage of a plurality of second input voltages of the second amplifier stage, wherein the common-mode voltage is produced after the operational amplifier is turned on;
a second common-mode feedback circuit, coupled to the first amplifier stage, the second common-mode feedback circuit configured to keep an output common-mode voltage of the first output voltages of the first amplifier stage at a reference voltage, wherein the voltage generated by the bias circuit serves as the reference voltage;
and
a plurality of switches, configured to control connection between the first amplifier stage, the second amplifier stage, the first output stage circuit, the second output stage circuit, the first common-mode feedback circuit, the logic loop circuit and the second common-mode feedback circuit to enable the operational amplifier to operate in an offset calibration phase.

6 more elements

A control method for offset calibration of an operational amplifier, the operational amplifier comprising a first amplifier stage, a second amplifier stage, a second output stage circuit, a first common-mode feedback circuit and a logic loop circuit, the control method comprising:

utilizing the first amplifier stage to generate a plurality of first output voltages according to a plurality of first input voltages;
utilizing the second amplifier stage, coupled to the first amplifier stage, to generate a plurality of second output voltages according to the first output voltages;
utilizing the second output stage circuit to be coupled to the second amplifier stage and a first output stage circuit;
when the offset calibration is performed, utilizing the first common-mode feedback circuit to keep an output common-mode voltage of the second output stage circuit at a predetermined value;
and
utilizing the logic loop circuit to adjust a difference between the first output voltages of the first amplifier stage to be close to zero.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/659,316Filed 21 Oct 2019
Priority: 12 Apr 2018
Published: 13 Feb 2020
Term ends: Not estimatedThe source records don’t support an estimate.

Classification51 codes

H03F 1/303
Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters: using a switching device
H03F 3/45475
Characterised by the way of implementation of the active amplifying circuit in the differential amplifier: using IC blocks as the active…
H03F 1/305
Modifications of amplifiers to reduce influence of variations of temperature or supply voltage or other physical parameters: in case of switching…
H03F 1/34
Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements:…