Single controller automatic calibrating circuits for reducing or canceling offset voltages in operational amplifiers in an instrumentation amplifier

An automatic calibrating operational amplifier (op-amp) system, comprising:

• an instrumentation amplifier, comprising:
• at least one front-end amplifier circuit, comprising:
• a first front-end voltage input configured to receive a first input voltage on a first voltage input;
• a second front-end voltage input configured to receive a second input voltage on a second voltage input;
• at least one front-end auxiliary differential input pair;
• and
• at least one front-end voltage output;
• the at least one front-end amplifier circuit configured to generate at least one intermediate output voltage on the at least one front-end voltage output based on the first input voltage and the second input voltage, and at least one front-end offset voltage based on a plurality of calibration signals applied to the at least one front-end auxiliary differential input pair;
• a final-stage amplifier circuit comprising a final-stage op-amp, comprising:
• a first final-stage voltage input configured to receive a first final-stage input voltage, and a second final-stage voltage input coupled to a first resistor circuit node;
• a final-stage auxiliary differential input pair;
• and
• a final-stage voltage output;
• the final-stage op-amp configured to generate a final-stage output voltage on the final-stage voltage output based on the at least one first intermediate output voltage, and a final-stage offset voltage applied to the final-stage auxiliary differential input pair;
• and
• an automatic calibration circuit coupled to the final-stage voltage output of the instrumentation amplifier, the automatic calibration circuit comprising:
• a single successive approximation register (SAR) controller configured to successively generate a plurality of bit signals in response to a calibration mode signal on a calibration mode input indicating a calibration mode, wherein a value of each successive plurality of bit signals is based on the final-stage output voltage at the final-stage voltage output;
• and
• a digital-to-analog converter (DAC) comprising a calibration output coupled to at least one of the at least one front-end auxiliary differential input pair comprising a first front-end auxiliary differential input pair and a second front-end auxiliary differential input pair, and the final-stage auxiliary differential input pair, the DAC configured to:
• convert each successive plurality of bit signals into a plurality of analog calibration signals on the calibration output based on the final-stage output voltage in response to the calibration mode signal indicating the calibration mode;
• and
• apply the plurality of analog calibration signals on the calibration output in response to the calibration mode signal indicating an amplify mode to compensate for a composite offset voltage of the instrumentation amplifier.

An automatic calibrating operational amplifier (op-amp) system, comprising:

• a means for generating at least one intermediate output voltage on at least one front-end voltage output based on a first input voltage and a second input voltage in an instrumentation amplifier, and at least one front-end offset voltage coupled to at least one front-end auxiliary differential input pair;
• a means for generating a final-stage output voltage on a final-stage voltage output based on the at least one intermediate output voltage, and at least one final-stage offset voltage coupled to at least one final-stage auxiliary differential input pair;
• and
• a means for automatically calibrating comprising a calibration output coupled to at least one of the at least one front-end auxiliary differential input pair comprising a first front-end auxiliary differential input pair and a second front-end auxiliary differential input pair, and the at least one final-stage auxiliary differential input pair, the means for automatically calibration comprising a means for:
• successively generating a plurality of bit signals in response to a calibration mode signal indicating a calibration mode, wherein a value of each successive plurality of bit signals is based on the final-stage output voltage at the final-stage voltage output;
• converting each successive plurality of bit signals into an analog calibration signal comprising an offset voltage on the calibration output based on the final-stage output voltage, in response to the calibration mode signal indicating the calibration mode;
• and
• applying the analog calibration signal on the calibration output in response to the calibration mode signal indicating an amplify mode.

A method of automatically calibrating an offset voltage in an instrumentation amplifier, comprising:

• generating at least one intermediate output voltage on at least one front-end voltage output based on a first input voltage and a second input voltage, and at least one front-end offset voltage based on a calibration signal applied to at least one front-end auxiliary differential input pair;
• generating a final-stage output voltage on a final-stage voltage output based on the at least one intermediate output voltage, and a final-stage offset voltage based on the calibration signal applied to a final-stage auxiliary differential input pair;
• successively generating a plurality of bit signals in response to a calibration mode signal indicating a calibration mode, wherein a value of each successive plurality of bit signals is based on the final-stage output voltage at the final-stage voltage output;
• converting each successive plurality of bit signals into an analog calibration signal on a calibration output coupled to at least one of the at least one front-end auxiliary differential input pair comprising a first front-end auxiliary differential input pair and a second front-end auxiliary differential input pair, and the final-stage auxiliary differential input pair, based on the final-stage output voltage in response to the calibration mode signal indicating the calibration mode;
• and
• applying the analog calibration signal on the calibration output in response to the calibration mode signal indicating an amplify mode.