# US 12,007,358 B2 · Potentiostat with offset calibration > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,007,358 B2 - Document ID: US12007358B2 - Status: Granted - Kind: B2 - Application number: 16/948,409 - Filed: 2020-09-17 - Published: 2021-08-26 - Granted: 2024-06-11 - Earliest claimed: 2020-02-21 - Assignees: Semiconductor Components Industries, LLC - Applicants: Semiconductor Components Industries, LLC - Inventors: Moez Kanoun - Web page: https://patentgrep.com/patent/US12007358B2 ## CPC - G01N 27/4175: {Calibrating or checking the analyser} - G01N 27/4163: {checking the operation of, or calibrating, the measuring apparatus (G01N27/3274, G01N27/4175 and G01N33/0006 take precedence)} - H03F 3/347: in integrated circuits - H03F 2200/129: there being a feedback over the complete amplifier - H03F 2200/375: Circuitry to compensate the offset being present in an amplifier - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - H03F: AMPLIFIERS ## Abstract A rail-to-rail potentiostat may require an offset current in order to support a bidirectional work electrode current at a work electrode. This offset current may improve measurements of the work electrode current made a dual-slope analog-to-digital converter, especially when the work electrode current is small, but can also lead to inaccuracies (e.g., due to a temperature coefficient) if it is not properly calibrated. Accordingly, bidirectional potentiostat is disclosed that can be configured in a normal configuration for measurement of a work electrode current or a calibration configuration for measurement (i.e., calibration) of an offset current. The reconfigurability allows calibrations to be taken as needed, on a schedule, or as specified by a user. The reconfigurability can also allow for maintaining a work electrode voltage and a work electrode current during calibration so that an electrochemical experiment using a cell coupled to the bidirectional potentiostat is unaffected by the calibration. ## Claims ### Claim 1 A method for measuring a work electrode current, the method comprising: generating, using a potentiostat coupled to a work electrode, a first output current, the first output current including a work electrode current component and an offset current component, the offset current component generated by an offset current source of the potentiostat; converting the first output current to a first digital word; modifying the first digital word using a calibration factor stored in a memory to obtain a measurement of the work electrode current; detecting a calibration event; and performing a calibration to measure the offset current component by: reconfiguring the potentiostat for the calibration; generating, using the reconfigured potentiostat, a second output current, the second output current being a measurement of the offset current component; converting the second output current to a second digital word; and updating the calibration factor stored in the memory according to the second digital word. ### Claim 2 (depends on 1) The method for measuring a work electrode current according to claim 1, wherein the calibration event corresponds to a change in an operating condition of the potentiostat. ### Claim 3 (depends on 1) The method for measuring a work electrode current according to claim 1, wherein the calibration event corresponds to a schedule. ### Claim 4 (depends on 1) The method for measuring a work electrode current according to claim 1, wherein the calibration event corresponds to a user input. ### Claim 5 (depends on 1) The method for measuring the work electrode current according to claim 1, wherein performing the calibration includes: maintaining a work electrode voltage and a work electrode current at the work electrode while performing the calibration. ### Claim 6 (depends on 1) The method for measuring a work electrode current according to claim 1, wherein the calibration factor corresponds to a digital measurement of the offset current component generated by the offset current source. ### Claim 7 (depends on 1) The method for measuring a work electrode current according to claim 1, wherein the reconfiguring includes adjusting circuitry of a front-end portion of the potentiostat to measure the offset current component generated by the offset current source without altering a work electrode voltage of the potentiostat. ### Claim 8 (depends on 1) The method for measuring a work electrode current according to claim 1, wherein converting the first output current to a first digital word and converting the second output current to a second digital word is performed using a dual-slope analog-to-digital converter. ### Claim 9 (depends on 8) The method for measuring a work electrode current according to claim 8, wherein: the first digital word corresponds to a first number of clock cycles taken to charge a capacitor of the dual-slope analog-to-digital converter using the work electrode current component and the offset current component; and the second digital word corresponds to a second number of clock cycles taken to charge the capacitor of the dual-slope analog-to-digital converter using the offset current component. ### Claim 10 (depends on 9) The method for measuring a work electrode current according to claim 9, wherein the modifying the first digital word using a calibration factor stored in a memory to obtain a measurement of the work electrode current includes: subtracting the second number of clock cycles from the first number of clock cycles to obtain a third number of clock cycles taken to charge the capacitor of the dual-slope analog-to-digital converter using the work electrode current component. ### Claim 11 A method for configuring a potentiostat coupled to a cell, the method including: coupling a front-end portion of the potentiostat to a work electrode of the cell, the front-end portion including a first feedback amplifier and a replica feedback amplifier that are substantially identical; configuring the potentiostat in a normal configuration for measuring a work-electrode current, wherein the configuring the potentiostat in the normal configuration includes: coupling the first feedback amplifier to a sensing and digitizing portion of the potentiostat; and decoupling the replica feedback amplifier from the sensing and digitizing portion of the potentiostat; triggering a calibration of an offset current, the offset current added to the work-electrode current by the potentiostat; and configuring the potentiostat in a calibration configuration for measuring the offset current, wherein the configuring the potentiostat in the calibration configuration includes: decoupling the first feedback amplifier from the sensing and digitizing portion of the potentiostat; and coupling the replica feedback amplifier to the sensing and digitizing portion of the potentiostat. ### Claim 12 (depends on 11) The method according to claim 11, wherein measuring the work-electrode current includes: generating a first measurement of a charging period of a capacitor and a second measurement of a discharging period of the capacitor to digitize the work-electrode current. ### Claim 13 (depends on 11) The method according to claim 11, wherein triggering the calibration of the offset current includes detecting a calibration event. ### Claim 14 (depends on 11) The method according to claim 11, wherein: configuring the potentiostat in the normal configuration further includes: coupling an offset current source to the work electrode and the first feedback amplifier; and coupling a replica offset current source to the replica feedback amplifier; and configuring the potentiostat in the calibration configuration further includes: coupling the offset current source to the replica feedback amplifier; and coupling the replica offset current source to the work electrode and the first feedback amplifier. ### Claim 15 (depends on 14) The method according to claim 14, wherein: configuring the potentiostat in the normal configuration further includes: maintaining a work electrode voltage and the work-electrode current at the work electrode of the cell using the first feedback amplifier and the offset current source; and configuring the potentiostat in the calibration configuration further includes: maintaining the work electrode voltage and the work-electrode current at the work electrode of the cell using the first feedback amplifier and the replica offset current source. ### Claim 16 (depends on 14) The method according to claim 14, wherein: configuring the potentiostat in the normal configuration further includes: receiving a first output current including a work electrode current component and an offset current component at the sensing and digitizing portion; and configuring the potentiostat in the calibration configuration further includes: receiving a second output current including the offset current component at the sensing and digitizing portion. ### Claim 17 (depends on 16) The method according to claim 16, wherein: configuring the potentiostat in the normal configuration further includes: configuring the sensing and digitizing portion to use a calibration factor to remove the offset current component from the first output current in order to generate a measurement of the work-electrode current; and configuring the potentiostat in the calibration configuration further includes: create/update the calibration factor corresponding to the offset current component. ### Claim 18 (depends on 11) The method according to claim 11, wherein the potentiostat further includes: a current-conveyer portion coupled between the front-end portion and the sensing and digitizing portion, the current-conveyer portion including a first current mirror and a second current mirror. ### Claim 19 (depends on 18) The method according to claim 18, wherein the first current mirror and the second current mirror are each a cascode current mirror. ### Claim 20 (depends on 18) The method according to claim 18, wherein the first current mirror and the second current mirror each include a chopper. ### Claim 21 A method for calibrating a potentiostat coupled to a cell, the method including: detecting a calibration event, the calibration event corresponding to a change in an offset current generated by an offset current source of the potentiostat; configuring, in response to the calibration event, the potentiostat in a calibration configuration; measuring the offset current at an output of a digitizer of the potentiostat in the calibration configuration; determining a calibration factor corresponding to the offset current; and storing the calibration factor for use by the potentiostat in a normal configuration to remove the offset current from the output of the digitizer of the potentiostat in the normal configuration to obtain a measurement of a work-electrode current. ### Claim 22 (depends on 21) The method according to claim 21, wherein the calibration event includes a change in an operating condition of the potentiostat. ### Claim 23 (depends on 21) The method according to claim 21, wherein the configuring, in response to the calibration event, the potentiostat includes enabling circuits of the potentiostat to measure the offset current without altering a work electrode voltage of the potentiostat.