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US 9,853,611 B2Granted
Instrumentation amplifier with digitally programmable input capacitance cancellation
AssigneeNortheastern University
InventorsChun-hsiang Chang, Marvin Onabajo
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Abstract
An instrumentation amplifier that includes input capacitance cancellation is provided. The architecture includes programmable capacitors between the input stage and a current feedback loop of the instrumentation amplifier to cancel input capacitances from electrode cables and a printed circuit board at the front end. An on-chip calibration unit can be employed to calibrate the programmable capacitors and improve the input impedance.
Claims16
An instrumentation amplifier device comprising:
- an instrumentation amplifier comprising:
- a differential input stage comprising an inverting input terminal and a non-inverting input terminal;
- an output stage driven by the input stage;
- a direct current feedback loop from the output stage to the input stage;
- and
- a negative capacitance generation feedback circuit between the input stage and the direct current feedback loop, wherein a negative capacitance is generated at the input stage to cancel parasitic capacitances at the inverting input terminal and the non-inverting input terminal and thereby boost input impedance, wherein the negative capacitance generation feedback circuit comprises:
- a first negative impedance converter circuit connected in parallel between the inverting input terminal and a first internal node of the instrumentation amplifier;
- and
- a second negative impedance converter circuit connected in parallel between the non-inverting terminal and a second internal node of the instrumentation amplifier.
6 more elements
An instrumentation amplifier device, comprising:
- an instrumentation amplifier comprising:
- a differential input stage comprising an inverting input terminal and a non-inverting input terminal;
- an output stage driven by the input stage;
- a direct current feedback loop from the output stage to the input stage;
- a negative capacitance generation feedback circuit between the input stage and the direct current feedback loop, and including programmable capacitors to generate the negative capacitance at the inverting input terminal and the non-inverting input terminal of the instrumentation amplifier;
- and
- a calibration circuit comprising a processor operative in a calibration mode to:
- measure voltage at an output node of the instrumentation amplifier or of a subsequent gain or filtering stage;
- compare the measured voltage amplitude to a plurality of reference voltages;
- generate a respective plurality of control signals responsive to the comparison;
- and
- transmit the generated control signals to control the programmable capacitors of the instrumentation amplifier to optimize the negative capacitance generated at the input terminals of the instrumentation amplifier.
9 more elements
A method of measuring biosignals comprising:
- receiving biosignals at an input stage of an instrumentation amplifier, the input stage including an inverting input terminal and a non-inverting input terminal;
- generating an amplified output signal at an output stage of the instrumentation amplifier;
- generating within the instrumentation amplifier a feedback loop from the output stage to the input stage;
- and
- boosting impedance at the input stage by generating a negative capacitance in the feedback loop from a first negative impedance converter circuit connected in parallel between the inverting input terminal and a first internal node of the instrumentation amplifier and a second negative impedance converter circuit connected in parallel between the non-inverting terminal and a second internal node of the instrumentation amplifier.
2 more elements
A method of measuring biosignals comprising:
- receiving biosignals at an input stage of an instrumentation amplifier, the input stage including an inverting input terminal and a non-inverting input terminal;
- generating an amplified output signal at an output stage of the instrumentation amplifier;
- generating within the instrumentation amplifier a feedback loop from the output stage to the input stage;
- boosting impedance at the input stage by generating a negative capacitance in the feedback loop;
- connecting electrode cables to the input stage of the instrumentation amplifier;
- and
- calibrating the negative capacitance converter circuitry after connecting the electrode cables to maximize the boosting of the impedance at the input stage.
4 more elements
An instrumentation amplifier device comprising:
- an instrumentation amplifier comprising
- a differential input stage comprising an inverting input terminal and a non-inverting input terminal;
- an output stage driven by the input stage;
- a direct current feedback loop from the output stage to the input stage;
- and
- a negative capacitance generation feedback circuit between the input stage and the direct current feedback loop, wherein a negative capacitance is generated at the input stage to cancel parasitic capacitances at the inverting input terminal and the non-inverting input terminal and thereby boost input impedance at the inverting input terminal and the non-inverting input terminal;
- wherein the negative capacitance generation feedback circuit is connected in parallel between the input stage and internal nodes of the instrumentation amplifier, and gains from the internal nodes are out of phase, creating a differential-mode signal.
4 more elements
Dependencies are inferred from the claim text.