Operational amplifier
AssigneeAnalog Devices Global
InventorsSharad Vijaykumar, Gerard Mora-Puchalt
Life of this patent
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Abstract
The amplifier circuit includes a pair of differential input stages coupled to an output stage where both a selected input stage and an unselected input stage are active with one of either a differential input signal or a reference voltage. A switching network couples a first input differential signal to a first differential input stage and a reference voltage to a second differential input stage when an amplifier input signal is less than a threshold voltage. The switching circuit also couples the second input differential signal to the second differential input stage and the reference voltage to the first differential input stage when the amplifier input signal is greater than the threshold signal.
Claims22
An amplifier circuit that generates an output voltage comprising a relatively constant offset voltage, the amplifier circuit comprising:
- an output stage configured to generate the output voltage;
- first and second differential input stages coupled to the output stage, wherein the first differential input stage includes a pair of first input transistors and the second differential input stage includes a pair of second input transistors complementary in type to the first input transistors;
- and
- a switching network configured to couple a differential input signal to the first differential input stage and a reference voltage to the second differential input stage in response to a control signal having a first state, and to couple the differential input signal to the second differential input stage and the reference voltage to the first differential input stage in response to the control signal having a second state.
An amplifier circuit that removes offset voltages from an output voltage, the circuit comprising:
- an output stage configured to generate the output voltage;
- first and second differential input stages coupled to the output stage, wherein the first differential input stage includes a pair of first input transistors and the second differential input stage includes a pair of second input transistors complementary in type to the first input transistors;
- a comparator circuit configured to generate a control signal;
- a switching network coupled to the comparator circuit and configured to select one of the first differential input stage or the second differential input stage by switching an input signal to the selected stage in response to the control signal, wherein an unselected stage of the first or second differential input stage is active;
- and
- circuitry configured to provide at least one of a chopper function or an auto-zero function that removes the offset voltage.
A method for signal amplification with offset voltage removal, the method comprising:
- switching a differential voltage to a pair of first input transistors of a first differential input stage;
- switching a reference voltage to a pair of second input transistors of a second differential input stage that is not coupled to the differential voltage while the differential voltage is coupled to the pair of first input transistors, wherein the second input transistors are complementary in type to the first input transistors;
- generating an amplifier output voltage in response to the differential voltage, the amplifier output voltage having an offset voltage;
- and
- removing the offset voltage from the amplifier output voltage.
Dependencies are inferred from the claim text.