Replica transistor voltage regulator

• US 8,080,984 B1
• Filed: 05/21/2008
• Issued: 12/20/2011
• Est. Priority Date: 05/22/2007
• Status: Active Grant

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Cypress Semiconductor Corporation (Infineon Technologies AG)
• Inventors: Geynet, Lionel
• Primary Examiner(s): Han, Jessica
• Application Number:
  US12/154,169
• Time in Patent Office: 1,308 Days
• Field of Search: 323312-317, 323/269, 323273-275, 323/280, 327538-543
• US Class Current: 323/280
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence

Abstract

A voltage regulator is provided having high accuracy, low PSRR, and no headroom limitation. Generally, the regulator includes: an operational amplifier (OPAMP) having a non-inverting input coupled to a reference voltage; an output source follower coupled to and controlled by an output of the OPAMP, the output source follower including a drain coupled to a voltage source and a source coupled to an output-node of the regulator; a replica source follower coupled to and controlled by the OPAMP, the replica source follower including a drain coupled to the voltage source and a source coupled to circuit ground through a resistor network; and a feedback circuit extending from the output-node through a feedback resistor to the source of the replica source follower and through at least a first resistor of the resistor network to an inverting input of the OPAMP to couple a feedback voltage thereto. Other embodiments are also provided.

Claims

1. A voltage regulator comprising:

an operational amplifier (OPAMP) having a non-inverting input coupled to a reference voltage (Vref);

an output source follower coupled to and controlled by an output of the OPAMP, the output source follower including a drain coupled to a voltage source and a source coupled to an output-node of the voltage regulator;

a replica source follower coupled to and controlled by the output of the OPAMP in parallel with the output source follower, the replica source follower including a drain coupled to the voltage source and a source coupled to a circuit ground through a resistor network; and

a feedback circuit extending from the output-node through a feedback resistor to the source of the replica source follower and through at least a first resistor of the resistor network to an inverting input of the OPAMP to couple a feedback voltage (Vfbk) thereto to regulate a voltage (Vout) at the output-node in response to a comparison between Vfbk and Vref.

2. A voltage regulator according to claim 1, wherein the feedback resistor comprises a resistance equal to or less than about 100 Ohms.

3. A voltage regulator according to claim 1, wherein the voltage regulator is a replica transistor voltage regulator comprising a replica leg including the replica source follower and the resistor network, and an output leg comprising the output source follower and further comprising a leaker transistor coupled between the source of the output source follower and circuit ground.

4. A voltage regulator according to claim 3, wherein the leaker transistor comprises a drain coupled to the source of the output source follower and a source coupled to circuit ground, and wherein the leaker transistor is controlled by a bias voltage to leak current from the output-node to provide at least a constant minimum current flow in the output source follower.

5. A voltage regulator according to claim 1, wherein the voltage regulator has a Vout that varies by 4.5% or less from a predetermined Vout.

6. A voltage regulator according to claim 1, wherein the voltage regulator has a power supply rejection ratio (PSRR) equal to or less than about −

20 decibels (dB).

7. A voltage regulator according to claim 1, wherein the voltage regulator has maximum headroom of at least 280 millivolts (mV).

8. A voltage regulator according to claim 1, wherein the voltage regulator utilizes a small area on a substrate on which it is implemented, having an area of less than about 100K microns (μ

m2).

9. A voltage regulator comprising:

an operational amplifier (OPAMP) having a non-inverting input coupled to a predetermined reference voltage (Vref);

an output source follower coupled to and controlled by an output of the OPAMP, the output source follower including a drain coupled to a voltage source and a source coupled to an output-node of the voltage regulator;

a replica source follower coupled to and controlled by the output of the OPAMP in parallel with the output source follower, the replica source follower including a drain coupled to the voltage source and a source coupled to a circuit ground through a resistor network; and

a feedback circuit extending from the output-node through a feedback transistor to the source of the replica source follower and through at least a first resistor of the resistor network to an inverting input of the OPAMP to couple a feedback voltage (Vfbk) thereto to regulate a voltage (Vout) at the output-node in response to a comparison between Vfbk and Vref.

10. A voltage regulator according to claim 9, wherein the feedback transistor is controlled by a biasing voltage that can be varied to adjust a magnitude of Vfbk.

11. A voltage regulator according to claim 10, wherein the feedback transistor is connected as a source follower having a source coupled to the source of the replica source follower and a drain coupled to the source of the output source follower.

12. A voltage regulator according to claim 11, wherein the feedback transistor further comprises a bulk terminal coupled to the source thereof to improve the stability of the feedback circuit.

13. A voltage regulator according to claim 9, wherein the voltage regulator is a replica transistor voltage regulator comprising a replica leg including the replica source follower and the resistor network, and an output leg comprising the output source follower and further comprising a leaker transistor coupled between the source of the output source follower and circuit ground to provide at least a constant minimum current flow in the output source follower.

14. A voltage regulator according to claim 9, wherein the voltage regulator has a Vout that varies by 4.5% or less from a predetermined Vout.

15. A voltage regulator according to claim 9, wherein the voltage regulator has a power supply rejection ratio (PSRR) equal to or less than about −

20 decibels (dB).

16. A voltage regulator according to claim 9, wherein the voltage regulator has maximum headroom of at least 280 millivolts (mV).

17. A voltage regulator according to claim 9, wherein the voltage regulator utilizes a small area on a substrate on which it is implemented, having an area of less than about 100K microns (μ

m2).

18. A method for operating a voltage regulator comprising:

coupling a reference voltage (Vref) to a non-inverting input of an operational amplifier (OPAMP);

controlling with a voltage (Vgate) from an output of the OPAMP an output source follower coupled thereto, the output source follower including a drain coupled to a voltage source and a source coupled to an output-node of the voltage regulator;

controlling with Vgate a replica source follower coupled to the output of the OPAMP in parallel with the output source follower, the replica source follower including a drain coupled to the voltage source and a source coupled to a circuit ground through a resistor network; and

coupling a feedback voltage (Vfbk) from the output-node to an inverting input of the OPAMP through a feedback circuit extending through at least a first resistor of the resistor network to regulate a voltage (Vout) at the output-node in response to a comparison between Vfbk and Vref, wherein the feedback circuit comprises a feedback resistor coupled between the output-node and the source of the replica source follower.

19. A method for operating a voltage regulator comprising:

coupling a reference voltage (Vref) to a non-inverting input of an operational amplifier (OPAMP);

controlling with a voltage (Vgate) from an output of the OPAMP an output source follower coupled thereto, the output source follower including a drain coupled to a voltage source and a source coupled to an output-node of the voltage regulator;

controlling with Vgate a replica source follower coupled to the output of the OPAMP in parallel with the output source follower, the replica source follower including a drain coupled to the voltage source and a source coupled to a circuit ground through a resistor network; and

coupling a feedback voltage (Vfbk) from the output-node to an inverting input of the OPAMP through a feedback circuit extending through at least a first resistor of the resistor network to regulate a voltage (Vout) at the output-node in response to a comparison between Vfbk and Vref, wherein the feedback circuit comprises a feedback transistor coupled between the output-node and the source of the replica source follower and controlled by a biasing voltage that can be varied to adjust a magnitude of Vfbk.