Common mode rejection ratio trim circuit and methodology
AssigneeLinear Technology Corporation
InventorHengsheng Liu
Life of this patent
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Abstract
An operational amplifier circuit includes an input differential circuit and a trim circuit for sensing the operational amplifier's input common mode voltage and generating an offset correction voltage in response thereto. The trim circuit reduces the amplifier's offset voltage dependence on input common mode voltage, and hence improves the common mode rejection ratio of the operational amplifier circuit.
Claims26
A method of improving CMRR in an amplifier having an offset voltage, comprising the steps of:
- generating an offset correction voltage that varies in response to an input common mode voltage of the amplifier having a differential input circuit including first and second transistors;
- and
- applying the offset correction voltage to drains of the first and second transistors to reduce dependence of the offset voltage from the input common mode voltage.
An operational amplifier circuit having improved CMRR performance, comprising:
- a differential input circuit including first and second transistors, and
- a trim circuit configured to sense an input common mode voltage of the amplifier and produce an offset correction voltage that varies in response thereto, the offset correction voltage being applied to drains of the first and second transistors.
An operational amplifier circuit having improved CMRR performance, comprising:
- a differential input circuit,
- a trim circuit configured to sense an input common mode voltage of the amplifier and produce an offset correction voltage that varies in response thereto, and
- a multiplexer connected to set the sign of the offset correction voltage,
- wherein the trim circuit comprises a differential amplifier circuit having first and second non-inverting inputs connected to respective differential inputs of the operational amplifier circuit, and an inverting input and an output connected to a voltage scaling circuit, and
- the differential amplifier circuit comprises a first differential circuit responsive to the first non-inverting input and the inverting input, and a second differential circuit responsive to the second non-inverting input and the inverting input.
An operational amplifier circuit having improved CMRR performance, comprising:
- a differential input circuit,
- a trim circuit configured to sense an input common mode voltage of the amplifier and produce an offset correction voltage that varies in response thereto, and
- a multiplexer connected to set the sign of the offset correction voltage,
- wherein the trim circuit comprises a differential amplifier circuit having first and second non-inverting inputs connected to respective differential inputs of the operational amplifier circuit, and an inverting input and an output connected to a voltage scaling circuit, and
- the differential amplifier circuit comprises multiple stages.
An operational amplifier circuit having improved CMRR performance, comprising:
- a differential input circuit,
- a trim circuit configured to sense an input common mode voltage of the amplifier and produce an offset correction voltage that varies in response thereto, and
- a multiplexer connected to set the sign of the offset correction voltage,
- wherein the trim circuit comprises a differential amplifier circuit having first and second non-inverting inputs connected to respective differential inputs of the operational amplifier circuit, and an inverting input and an output connected to a voltage scaling circuit, and
- the trim circuit comprises a second differential circuit for generating the offset correction voltage to the differential input circuit.
Dependencies are inferred from the claim text.