Voltage reference circuit using differential feedback

1 . An apparatus, comprising:

a driver circuit configured to generate an output current using a control signal, wherein a value of the output current is based on a voltage level of the 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 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 asymmetric differential amplifier circuit is configured to:

receive, at a gate terminal of the first transistor, the reference voltage;

receive, at a gate terminal of the second transistor, the feedback voltage; and

generate the voltage level of the control signal based on a difference between the first threshold voltage and the second threshold voltage.

2 . The apparatus of claim 1 , wherein the first transistor is a metal-oxide semiconductor field-effect transistor configured to operate in a sub-threshold region, and wherein the second transistor is a metal-oxide semiconductor field-effect transistor configured to operate in the sub-threshold region.

3 . The apparatus of claim 2 , wherein the asymmetric differential amplifier circuit includes a current mirror circuit coupled to the first transistor and the second transistor, wherein the current mirror circuit is configured to provide a first current to the first transistor and a second current to the second transistor.

4 . The apparatus of claim 3 , wherein a first value of the first current is a same value as a second value of the second current, and wherein a first width-to-length ratio of the first transistor is different than a second width-to-length ratio of the second transistor.

5 . The apparatus of claim 3 , wherein a first value of the first current is different than a second value of the second current, and wherein a first width-to-length ratio of the first transistor is a same value as a second width-to-length ratio of the second transistor.

6 . The apparatus of claim 1 , wherein the divider circuit includes a plurality of resistors coupled between the driver 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.

7 . A method, comprising:

generating, by a driver circuit, an output current using a control signal, wherein a value of the output current is based on a voltage level of the control signal;

generating, by a divider circuit using the output current, a feedback voltage and a reference voltage; and

asymmetrically amplifying, by a differential amplifier circuit, a difference between the reference voltage and the feedback voltage to generate the control signal, wherein the differential amplifier circuit includes a first transistor with a first threshold voltage and a second transistor with a second threshold voltage different than the first threshold voltage, and wherein asymmetrically amplifying the difference between the reference voltage and the feedback voltage includes:

controlling a conductance of the first transistor using the reference voltage;

controlling a conductance of the second transistor using the feedback voltage; and

generating the voltage level of the control signal based on a difference between the first threshold voltage and the second threshold voltage.

8 . The method of claim 7 , wherein the first transistor and the second transistor are metal-oxide semiconductor field-effect transistors, and wherein asymmetrically amplifying the difference between the reference voltage and the feedback voltage includes operating the first transistor and the second transistor in a sub-threshold region of operation.

9 . The method of claim 7 , wherein asymmetrically amplifying the difference between the reference voltage and the feedback voltage further includes establishing a first current density in the first transistor and a second current density in the second transistor, wherein the second current density is different than the first current density.

10 . The method of claim 9 , wherein a first width-to-length ratio of the first transistor is different than a second width-to-length ratio of the second transistor, wherein establishing the first current density in the first transistor and the second current density in the second transistor includes providing, by a current mirror circuit, a first current to the first transistor and a second current to the second transistor, and wherein a first value of the first current is a same value as a second value of the second current.

11 . The method of claim 9 , wherein a first width-to-length ratio of the first transistor is a same value as a second width-to-length ratio of the second transistor, wherein establishing the first current density in the first transistor and the second current density in the second transistor includes providing, by a current mirror circuit, a first current to the first transistor and a second current to the second transistor, and wherein a first value of the first current is different than a second value of the second current.

12 . The method of claim 7 , wherein the divider circuit includes at least a first resistor and a second resistor coupled in series between the driver circuit and a ground supply node.

13 . The method of claim 12 , further comprising adjusting, based on a trim signal, a value of at least one of the first resistor or the second resistor.

14 . An apparatus, comprising:

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:

source, based on a control signal, an output current to the reference node;

generate a feedback voltage and a reference voltage on the reference node using the output current;

control a conductance of the first transistor using the reference voltage;

control a conductance of the second transistor using the feedback voltage; and

amplify, based on the difference between the first and second threshold voltages, a difference between the reference voltage and the feedback voltage to generate the control signal.

15 . The apparatus of claim 14 , wherein the first transistor and the second transistor are metal-oxide semiconductor field-effect transistors, and wherein to amplify the difference between the reference voltage and the feedback voltage, the voltage reference circuit is further configured to operate the first transistor and the second transistor in a sub-threshold region of operation.

16 . The apparatus of claim 14 , wherein to amplify the difference between the reference voltage and the feedback voltage, the voltage reference circuit is further configured to establish a first current density in the first transistor and a second current density in the second transistor, wherein the second current density is different than the first current density.

17 . The apparatus of claim 16 , wherein a first width-to-length ratio of the first transistor is different than a second width-to-length ratio of the second transistor, wherein to establish the first current density in the first transistor and the second current density in the second transistor, the voltage reference circuit is further configured to provide a first current to the first transistor and a second current to the second transistor, and wherein a first value of the first current is a same value as a second value of the second current.

18 . The apparatus of claim 16 , wherein a first width-to-length ratio of the first transistor is a same value as a second width-to-length ratio of the second transistor, wherein to establish the first current density in the first transistor and the second current density in the second transistor, the voltage reference circuit is further configured to provide a first current to the first transistor and a second current to the second transistor, and wherein a first value of the first current is different than a second value of the second current.

19 . The apparatus of claim 14 , wherein the voltage reference circuit includes at least a first resistor and a second resistor coupled in series between the reference node and a ground supply node.

20 . The apparatus of claim 19 , wherein the voltage reference circuit is further configured to adjust, based on a trim signal, a value of at least one of the first resistor or the second resistor.