# US 10,117,591 B2 · Impedance bootstrap circuit for an interface of a monitoring device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,117,591 B2 - Document ID: US10117591B2 - Status: Granted - Kind: B2 - Application number: 14/882,911 - Filed: 2015-10-14 - Published: 2016-03-10 - Granted: 2018-11-06 - Earliest claimed: 2012-05-22 - Assignees: Stryker Corporation - Applicants: Stryker Corporation - Inventors: Randall Jeffrey Krohn - Web page: https://patentgrep.com/patent/US10117591B2 ## CPC - A61B 5/305: Common mode rejection - A61B 5/6801: {specially adapted to be attached to or worn on the body surface} - A61B 5/7203: {for noise prevention, reduction or removal} - H03F 1/56: Modifications of input or output impedances, not otherwise provided for - H03F 3/45968: {by offset reduction} - H03F 2200/261: Amplifier which being suitable for instrumentation applications - H03F 2203/45138: Two or more differential amplifiers in IC-block form are combined, e.g. measuring amplifiers - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - H03F: AMPLIFIERS ## Abstract An interface for receiving electrical signals representative of a condition of a patient and for conveying representations of the electrical signals to a processing system. The interface includes at least one amplifier circuit configured to alter an amplitude of the electrical signal, a common-mode cancellation amplifier circuit coupled to the at least one amplifier circuit and configured to reduce common-mode signal noise in the electrical signals, and a bootstrap circuit coupled to the at least one amplifier circuit and configured to increase an effective input impedance at an input of the at least one amplifier circuit. ## Claims ### Claim 1 An interface being connectable between a processing system and a sensor being attachable to a patient, said interface comprising: a circuit being configured to detect an error condition comprising at least one of (1) the sensor being disconnected from said interface and (2) the sensor being detached from the patient, the circuit includes an amplifier including inputs and wherein a path is defined between the sensor and said amplifier and wherein said circuit detects said error condition by monitoring impedance of said path, wherein said circuit is configured to actively provide a feedback condition recognizable by the processing system in response to detecting that said error condition is present such that the processing system generates an indication being informative of said error condition; and a bootstrap circuit coupled to said inputs of said amplifier and wherein said circuit further provides said feedback condition by increasing an effective input impedance at said inputs of said amplifier using said bootstrap circuit in response to determining that said error condition is present. ### Claim 2 (depends on 1) The interface of claim 1 wherein impedance of said path has a first value when said error condition is absent and a second value when said error condition is present and wherein said second value is greater than said first value and wherein said circuit detects said error condition when impedance of said path has said second value. ### Claim 3 An interface being connectable between a processing system and a sensor being attachable to a patient, said interface comprising: a circuit being configured to detect an error condition comprising at least one of (1) the sensor being disconnected from said interface and (2) the sensor being detached from the patient, the circuit includes an amplifier including inputs and wherein a path is defined between the sensor and said amplifier and wherein said circuit detects said error condition by monitoring impedance of said path, wherein said circuit is configured to actively provide a feedback condition recognizable by the processing system in response to detecting that said error condition is present such that the processing system generates an indication being informative of said error condition, said circuit further provides said feedback condition by driving said inputs of said amplifier above a predetermined maximum input range of said amplifier in response to determining that said error condition is present. ### Claim 4 (depends on 3) The interface of claim 3 wherein said circuit further provides said feedback condition by latching said inputs of said amplifier in response to driving said inputs above said predetermined maximum input range. ### Claim 5 (depends on 4) The interface of claim 4 wherein said circuit further provides said feedback condition by causing an output of said amplifier to be non-responsive to input conditions into said amplifier as a result of latching said inputs. ### Claim 6 (depends on 3) The interface of claim 3 wherein said circuit further comprises an impedance check circuit coupled to said inputs of said amplifier and wherein said impedance check circuit drives said inputs of said amplifier above said predetermined maximum input range to provide said feedback condition. ### Claim 7 (depends on 6) The interface of claim 6 wherein a common-mode cancellation path is defined through said impedance check circuit and wherein said impedance check circuit is configured to tune said common-mode cancellation path for driving said inputs of said amplifier above said predetermined maximum input range. ### Claim 8 (depends on 5) The interface of claim 5 wherein said circuit is further configured to actively remove said feedback condition in response to detecting that said error condition is no longer present. ### Claim 9 (depends on 8) The interface of claim 8 wherein said circuit removes said feedback condition by driving said inputs of said amplifier at or below said predetermined maximum input range of said amplifier in response to determining that said error condition is no longer present. ### Claim 10 (depends on 9) The interface of claim 9 wherein said circuit further removes said feedback condition by unlatching said inputs of said amplifier in response to driving said inputs at or below said predetermined maximum input range. ### Claim 11 (depends on 10) The interface of claim 10 wherein said circuit further removes said feedback condition by causing said output of said amplifier to be responsive to input conditions into said amplifier as a result of unlatching said inputs. ### Claim 12 A method of operating a system including a processing system, a sensor being attachable to a patient, and an interface being connectable between the processing system and the sensor, the method comprising: detecting with the interface an error condition comprising at least one of (1) the sensor being disconnected from the interface and (2) the sensor being detached from the patient; actively providing with the interface a feedback condition in response to detecting that the error condition is present; recognizing with the processing system the feedback condition; and generating with the processing system an indication being informative of the error condition, the circuit further comprises an amplifier including inputs and a path defined between the sensor and the amplifier and wherein the step of detecting the error condition further comprises monitoring impedance of the path, the step of providing the feedback condition further comprises increasing an effective input impedance at the inputs of the amplifier in response to determining that the error condition is present. ### Claim 13 (depends on 12) The method of claim 12 wherein the step of providing the feedback condition further comprises driving the inputs of the amplifier above a predetermined maximum input range of the amplifier in response to determining that the error condition is present. ### Claim 14 (depends on 13) The method of claim 13 wherein the step of providing the feedback condition further comprises latching the inputs of the amplifier in response to driving the inputs above the predetermined maximum input range. ### Claim 15 (depends on 14) The method of claim 14 wherein the step of providing the feedback condition further comprises causing an output of the amplifier to be non-responsive to input conditions into the amplifier as a result of latching the inputs. ### Claim 16 A method of operating a system including a processing system, a sensor being attachable to a patient, and an interface being connectable between the processing system and the sensor, the method comprising: detecting with the interface an error condition comprising at least one of (1) the sensor being disconnected from the interface and (2) the sensor being detached from the patient; actively providing with the interface a feedback condition in response to detecting that the error condition is present; recognizing with the processing system the feedback condition; generating with the processing system an indication being informative of the error condition, wherein the circuit further comprises an amplifier including inputs and a path defined between the sensor and the amplifier and wherein the step of detecting the error condition further comprises monitoring impedance of the path; and actively removing the feedback condition in response to detecting that the error condition is no longer present. ### Claim 17 (depends on 16) The method of claim 16 wherein the step of removing the feedback condition is further defined as driving the inputs of the amplifier at or below the predetermined maximum input range of the amplifier, unlatching the inputs of the amplifier in response to driving the inputs at or below the predetermined maximum input range, and causing the output of the amplifier to be responsive to input conditions into the amplifier as a result of unlatching the inputs.