# US 12,009,847 B2 · Split input amplifier for protection from DC offset > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,009,847 B2 - Document ID: US12009847B2 - Status: Granted - Kind: B2 - Application number: 17/950,053 - Filed: 2022-09-21 - Published: 2023-09-14 - Granted: 2024-06-11 - Earliest claimed: 2022-03-09 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Hongrui Wang; Abbas Komijani; Xinhua Chen - Web page: https://patentgrep.com/patent/US12009847B2 ## CPC - H03F 1/52: Circuit arrangements for protecting such amplifiers {(monitoring arrangements G01R31/28; increasing reliability in communication systems, e.g. using redundancy H04B1/74)} - H04B 1/04: Circuits - H03F 1/301: {in MOSFET amplifiers (H03F1/303, H03F1/305, H03F1/308 take precedence)} - H03F 3/187: in integrated circuits - H03F 3/45183: {Long tailed pairs (H03F3/4521, H03F3/45237 take precedence)} - H03F 3/45744: {by offset reduction} - H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)} - H03F 2203/45212: the differential amplifier being designed to have a reduced offset - H03F 2203/45588: the IC comprising offset compensating means - H04B 2001/0408: {with power amplifiers} - H04B 2001/0416: {having gain or transmission power control} - H03F: AMPLIFIERS - H04B: TRANSMISSION ## Abstract Embodiments presented herein provide apparatus and techniques to reduce a direct current (DC) voltage offset between a transmitter and receiver. Embodiments include a shared reference voltage signal generated by a reference voltage source. The receiver may include a first unit gain buffer to receive a reference voltage signal from the reference voltage source. The transmitter may be communicatively coupled to the receiver via one or more connections and may include a second unit gain buffer communicatively coupled to the first unit gain buffer via one of the connections. An amplifier (e.g., an operation amplifier) of the transmitter may include multiple positive inputs coupled to the second unit gain buffer and an offset tracker. The offset tracker may compensate for a DC offset caused by at least a power supply and/or a ground bounce. ## Claims ### Claim 1 An electronic device, comprising: a receiver configured to generate a reference voltage signal; a transmitter coupled to the receiver, the transmitter comprising: a differential amplifier configured to receive the reference voltage signal via the receiver and a varying power supply; and offset tracking circuitry coupled to the differential amplifier, the offset tracking circuitry configured to compensate for a direct current voltage offset based at least partially on a comparison of the reference voltage signal and the varying power supply. ### Claim 2 (depends on 1) The electronic device of claim 1, wherein the receiver comprises a first unit gain buffer, the transmitter comprises a second unit gain buffer, and the first unit gain buffer is coupled to the second unit gain buffer via a connector. ### Claim 3 (depends on 2) The electronic device of claim 2, wherein the receiver comprises a voltage source coupled to a positive input of the first unit gain buffer, the voltage source configured to generate the reference voltage signal. ### Claim 4 (depends on 1) The electronic device of claim 1, wherein the differential amplifier comprises an input resistor and a feedback resistor, the differential amplifier configured to receive an input value based on a first resistance of the input resistor and a second resistance of the feedback resistor. ### Claim 5 (depends on 4) The electronic device of claim 4, wherein the input value is indicative of the first resistance of the input resistor divided by a sum of the first resistance of the input resistor and the second resistance of the feedback resistor. ### Claim 6 (depends on 1) The electronic device of claim 1, wherein the receiver further comprises a multiplexer coupled to an output of the differential amplifier, the multiplexer configured to multiplex a control signal with an intermediate frequency signal. ### Claim 7 (depends on 6) The electronic device of claim 6, wherein the multiplexer comprises a high pass filter and a low pass filter. ### Claim 8 A transmitter, comprising: a differential amplifier configured to receive a reference voltage from a receiver and configured to receive a varying power supply; and offset tracking circuitry configured to couple to the differential amplifier, and compensate for a voltage offset by tracking a comparison of the varying power supply, the reference voltage, and a ground bounce associated with an electrical ground. ### Claim 9 (depends on 8) The transmitter of claim 8, wherein the differential amplifier comprises a first positive input and a second positive input. ### Claim 10 (depends on 8) The transmitter of claim 8, comprising a first unit gain buffer, wherein the first unit gain buffer is coupled to a second unit gain buffer of the receiver. ### Claim 11 (depends on 10) The transmitter of claim 10, comprising a first high pass filter coupled to the first unit gain buffer and a second high pass filter coupled to the second unit gain buffer. ### Claim 12 (depends on 11) The transmitter of claim 11, wherein the first high pass filter and the second high pass filter are configured to enable a data signal to propagate between the first unit gain buffer and the second unit gain buffer. ### Claim 13 (depends on 8) The transmitter of claim 8, wherein the differential amplifier is configured to receive a value that is indicative of a voltage between the varying power supply and the ground bounce. ### Claim 14 (depends on 8) The transmitter of claim 8, wherein the differential amplifier comprises a diplexer, a first set of amplification stages, and a second set of amplification stages, the diplexer configured to enable the first set of amplification stages to receive the reference voltage from the receiver and couple the second set of amplification stages to the offset tracking circuitry. ### Claim 15 (depends on 14) The transmitter of claim 14, wherein the first set of amplification stages comprises a first number of amplification stages, the second set of amplification stages comprises a second number of amplification stages, and the first number of amplification stages is greater than the second number of amplification stages. ### Claim 16 (depends on 14) The transmitter of claim 14, wherein an output of the diplexer is based on a control signal used to program an output of the offset tracking circuitry to compensate for the voltage offset. ### Claim 17 A transceiver, comprising: a receiver configured to generate a reference voltage signal; a transmitter coupled to the receiver, the transmitter comprising: a differential amplifier configured to compare the reference voltage signal and a power supply variation; and offset tracking circuitry coupled to the differential amplifier, the offset tracking circuitry configured to compensate for a direct current voltage offset based at least partially on the comparison of the reference voltage signal and the power supply variation. ### Claim 18 (depends on 17) The transceiver of claim 17, wherein the offset tracking circuitry is configured to track the power supply variation and a ground bounce. ### Claim 19 (depends on 18) The transceiver of claim 18, wherein the offset tracking circuitry is configured to compensate for the direct current voltage offset based at least partially on the ground bounce. ### Claim 20 (depends on 17) The transceiver of claim 17, wherein the receiver comprises a voltage source coupled to a first unit gain buffer and the transmitter comprises a second unit gain buffer, the second unit gain buffer configured to receive the reference voltage signal via the first unit gain buffer.