# US 12,216,484 B2 · Voltage reference circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,216,484 B2 - Document ID: US12216484B2 - Status: Granted - Kind: B2 - Application number: 18/340,759 - Filed: 2023-06-23 - Published: 2024-12-26 - Granted: 2025-02-04 - Earliest claimed: 2023-06-23 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Sechang Oh; Soheil Golara; Denis C. Daly; Seyedeh Sedigheh Hashemi; Mansour Keramat - Web page: https://patentgrep.com/patent/US12216484B2 ## CPC - G05F 1/468: {characterised by reference voltage circuitry, e.g. soft start, remote shutdown} - G05F 1/56: using semiconductor devices in series with the load as final control devices (G05F1/461 takes precedence) - G05F 3/262: {using field-effect transistors only} - G06F 1/26: Power supply means, e.g. regulation thereof (for memories G11C) - G05F: SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A voltage reference circuit included in a computer system includes an asymmetric amplifier circuit that includes two metal-oxide semiconductor field-effect transistors with different threshold voltages. The voltage reference circuit also includes an output circuit that generates, using a control signal, a bias signal and an output current that is used by a divider circuit to generate a reference voltage and a feedback voltage. The reference voltage and bias signal are used by the amplifier circuit to generate the control signal, which is based on a difference between the transistors' threshold voltages. ## Claims ### Claim 1 An apparatus, comprising: an output circuit configured to generate an output current and a bias signal using a control signal; a divider circuit configured to generate a feedback voltage and a reference voltage using the output current; and an asymmetric differential amplifier circuit including a first transistor and a second transistor manufactured according to a particular manufacturing process having a plurality of available threshold voltages, the first transistor having a first threshold voltage of the plurality of threshold voltages and the second transistor having a second, different threshold voltage of the plurality of threshold voltages, wherein the amplifier circuit is configured to generate the control signal using the feedback voltage, the bias signal, and a difference between the first threshold voltage and the second threshold voltage. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the first transistor is a metal-oxide semiconductor field-effect transistor configured to operate in a saturation region of operation, and wherein the second transistor is a metal-oxide semiconductor field-effect transistor configured to operate in the saturation region of operation. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the output circuit includes a startup circuit configured to initialize the bias signal during a startup operation. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein to initialize the bias signal, the startup circuit is further configured to discharge, based on a startup signal and the reference voltage, a bias node through which the bias signal propagates. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the output circuit includes a current mirror circuit, wherein to generate the output current, the output circuit is further configured to generate a first current using the control signal, and wherein the current mirror circuit is configured to generate the output current using the first current. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the divider circuit includes a plurality of resistors coupled between the output circuit and a ground supply node, and wherein the divider circuit is further configured to adjust a value of at least one resistor of the plurality of resistors using a trim control signal. ### Claim 7 A method, comprising: generating, by an output circuit, an output current using a control signal; generating, by the output circuit, a bias signal using the control signal; generating, by a divider circuit using the output current, a feedback voltage and a reference voltage; and generating, by a differential amplifier circuit that includes a first transistor and a second transistor manufactured according to a particular manufacturing process having a plurality of available threshold voltages, the first transistor having a first threshold voltage of the plurality of threshold voltages and the second transistor having a second, different threshold voltage of the plurality of threshold voltages, the control signal using the feedback voltage, the bias signal, and a difference between the first threshold voltage and the second threshold voltage. ### Claim 8 (depends on 7) The method of claim 7, wherein the first transistor and the second transistor are metal-oxide semiconductor field-effect transistors, and further comprising, biasing the first transistor and the second transistor to operate in a saturation region of operation. ### Claim 9 (depends on 7) The method of claim 7, further comprising initializing the bias signal during a startup operation. ### Claim 10 (depends on 9) The method of claim 9, wherein initializing the bias signal includes discharging a bias node in response to activating a startup signal, and in response to determining that the reference voltage is less than a threshold value. ### Claim 11 (depends on 7) The method of claim 7, wherein generating the output current includes: generating a first current using the control signal; and generating, by a current mirror circuit using the first current, the output current. ### Claim 12 (depends on 11) The method of claim 11, wherein generating the bias signal includes generating, by a current mirror circuit using the first current, a bias current for the first transistor and the second transistor. ### Claim 13 (depends on 7) The method of claim 7, further comprising adjusting, using a trim control signal, a value of a variable resistor through which the output current flows to modify a value of the reference voltage. ### Claim 14 An apparatus, comprising: a computer system that includes: a functional circuit block coupled to a reference node; and a voltage reference circuit that includes a first transistor with a first threshold voltage and a second transistor with a second threshold voltage different than the first threshold voltage, wherein the voltage reference circuit is configured to: generate an output current using a control signal; generate a bias signal using the control signal; generate, using the output current, a reference voltage on the reference node, and a feedback voltage; and generate the control signal using the feedback voltage, the bias signal, and a difference between the first threshold voltage and the second threshold voltage. ### Claim 15 (depends on 14) The apparatus of claim 14, wherein the first transistor and the second transistor are a metal-oxide semiconductor field-effect transistors, and wherein the voltage reference circuit is further configured to bias the first transistor and the second transistor to operate in a saturation region of operation. ### Claim 16 (depends on 14) The apparatus of claim 14, wherein the voltage reference circuit is further configured to initialize the bias signal during a startup operation, and wherein the functional circuit block and the voltage reference circuit are located on a common integrated circuit included in the computer system. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein to initialize the bias signal, the voltage reference circuit is further configured to discharge a bias node in response to an activation of a startup signal and in response to a determination that the reference voltage is less than a threshold value. ### Claim 18 (depends on 14) The apparatus of claim 14, wherein to generate the output current, the voltage reference circuit is further configured to generate a first current using the control signal, and wherein the voltage reference circuit includes a current mirror circuit configured to generate the output current using the first current. ### Claim 19 (depends on 18) The apparatus of claim 18, wherein the current mirror circuit is further configured to generate a bias current for the first transistor and the second transistor using the first current. ### Claim 20 (depends on 14) The apparatus of claim 14, wherein the voltage reference circuit includes a variable resistor through which the output current flows, and wherein the voltage reference circuit is further configured to adjust a value of the variable resistor using a trim control signal.