Voltage regulator
A method and apparatus are provided. The apparatus includes a plurality of devices forming a positive feedback loop for driving a regulated output voltage towards a reference voltage. Device ratios of at least two of the plurality of devices are set such that the positive feedback loop is stable.
1. An apparatus, comprising:
a plurality of devices forming a positive feedback loop for driving a regulated output voltage towards a reference voltage, the plurality of devices including:
a sensing element configured to sense a change in the regulated output voltage, and
a control element configured to generate a control signal in response to an indication of the sensed change in the regulated output voltage; and
a ratio of a transductance of the sensing element to a transductance of the control element being set to provide that the positive feedback loop is stable.
2. The apparatus of claim 1 wherein the control signal drives the regulated output voltage towards the reference voltage.
3. The apparatus of claim 1 wherein the plurality of devices comprises a current mirror configured to provide the indication of the sensed change to the control element.
4. The apparatus of claim 3 wherein the current mirror is configured to provide the indication of the sensed change by adjusting a current provided to the control element in response to the sensing element sensing a change in the regulated output voltage.
5. The apparatus of claim 3 wherein the current mirror comprises a first and second device and a relationship between a device ratio of the first device and a device ratio of the second device is such that the positive feedback loop is stable.
6. The apparatus of claim 1 wherein the plurality of devices are transistors and a device ratio corresponds to a gate width to length ratio of a device.
7. The apparatus of claim 1 wherein the ratios of the transconductance providing a stable loop gain provides a loop gain of the positive feedback loop to be less than one.
8. The apparatus of claim 1 wherein the apparatus is a voltage regulator.
9. A method, comprising:
driving a regulated output voltage towards a reference voltage by a positive feedback loop formed by a plurality of devices, the plurality of devices including a sensing element and a control element;
sensing by the sensing element a change in the regulated output voltage;
generating by the control element a control signal in response to an indication of the sensed change in the regulated output voltage; and
setting a ratios of transductance of the sensing element and the control element to provide that the positive feedback loop is stable.
10. The method of claim 9 wherein driving the regulated output voltage towards the reference voltage comprises driving the regulated output voltage towards the reference voltage by the control signal.
11. The method of claim 9 wherein the plurality of devices comprises a current mirror and the method further comprises:
providing the indication of the change to the control element by the current mirror.
12. The method of claim 11 , further comprising:
providing the indication of the change by adjusting a current provided to the control element in response to the sensing element sensing a change in the regulated output voltage.
13. The method of claim 11 wherein the current mirror comprises a first and second device and a relationship between a device ratio of the first device and a device ratio of the second device is such that the positive feedback loop is stable.
14. The method of claim 9 wherein the plurality of devices are transistors and a device ratio corresponds to a gate width to length ratio of a device.
15. The apparatus of claim 9 wherein the ratios of the transconductance providing a stable loop gain provides a loop gain of the positive feedback loop to be less than one.