Indirect leakage compensation for multi-stage amplifiers

1. A linear regulator, comprising:

a pass device coupled between an input voltage level and an output node;

a feedback loop for controlling the pass device based on a reference voltage and a feedback voltage that depends on an output voltage at the output node;

an off-state device that is kept in the off-state; and

a leakage compensation circuit for sinking a leakage compensation current from the output node, in dependence on a leakage current of the off-state device,

wherein the off-state device is coupled between the leakage compensation circuit and an intermediate voltage level of the linear regulator; and

wherein the intermediate voltage level is a voltage level between the input voltage level and ground, with a magnitude of the intermediate voltage level being smaller than a magnitude of the input voltage level.

2. The linear regulator according to claim 1 , wherein the leakage compensation circuit is adapted to generate the leakage compensation current by applying a gain to the leakage current of the off-state device.

3. The linear regulator according to claim 2 , wherein the gain depends on the leakage current of the off-state device.

4. The linear regulator according to claim 2 , wherein the gain is determined by a function that depends on the leakage current of the off-state device, a channel length of the pass device, and a channel length of the off-state device.

5. The linear regulator according to claim 4 , wherein the function further depends on a voltage across the pass device.

6. The linear regulator according to claim 1 , wherein the intermediate voltage level is a voltage level that depends on the feedback voltage.

7. The linear regulator according to claim 1 , wherein the off-state device differs from the pass device in at least one of a transistor type and a channel length.

8. The linear regulator according to claim 1 , wherein the feedback loop comprises an operational amplifier for controlling the pass device, the operational amplifier receiving, at its inputs, the reference voltage and the feedback voltage; and

wherein the intermediate voltage level is a common source voltage level of the operational amplifier.

9. The linear regulator according to claim 1 , wherein the feedback loop comprises an operational amplifier for controlling the pass device, the operational amplifier receiving, at its inputs, the reference voltage and the feedback voltage; and

wherein the intermediate voltage level is decoupled from the input voltage level by a transistor device of the operational amplifier that is pre-biased or whose gate terminal is coupled to a gate terminal of the pass device.

10. The linear regulator according to claim 1 , wherein the intermediate voltage level is the output voltage.

11. The linear regulator according to claim 1 , wherein the leakage compensation circuit comprises a current mirror and a biased transistor device coupled in series with one of the transistor devices of the current mirror.

12. A method of operating a linear regulator, wherein the linear regulator comprises:

a pass device coupled between an input voltage level and an output node; and

a feedback loop for controlling the pass device based on a reference voltage and a feedback voltage that depends on an output voltage at the output node,

the method comprising:

providing an off-state device that is kept in the off-state; and

sinking a leakage compensation current from the output node, by means of a leakage compensation circuit, in dependence on a leakage current of the off-state device,

wherein the off-state device is coupled between the leakage compensation circuit and an intermediate voltage level of the linear regulator; and

wherein the intermediate voltage level is a voltage level between the input voltage level and ground, with a magnitude of the intermediate voltage level being smaller than a magnitude of the input voltage level.

13. The method according to claim 12 , further comprising:

generating the leakage compensation current by applying a gain to the leakage current of the off-state device.

14. The method according to claim 13 , wherein the gain depends on the leakage current of the off-state device.

15. The method according to claim 13 , wherein the gain is determined by a function that depends on the leakage current of the off-state device, a channel length of the pass device, and a channel length of the off-state device.

16. The method according to claim 15 , wherein the function further depends on a voltage across the pass device.

17. The method according to claim 12 , wherein the intermediate voltage level is a voltage level that depends on the feedback voltage.

18. The method according to claim 12 , wherein the off-state device differs from the pass device in at least one of a transistor type and a channel length.

19. The method according to claim 12 , wherein the feedback loop comprises an operational amplifier for controlling the pass device, the operational amplifier receiving, at its inputs, the reference voltage and the feedback voltage; and

wherein the intermediate voltage level is a common source voltage level of the operational amplifier.

20. The method according to claim 12 , wherein the feedback loop comprises an operational amplifier for controlling the pass device, the operational amplifier receiving, at its inputs, the reference voltage and the feedback voltage; and

wherein the intermediate voltage level is decoupled from the input voltage level by a transistor device of the operational amplifier that is pre-biased or whose gate terminal is coupled to a gate terminal of the pass device.

21. The method according to claim 12 , wherein the intermediate voltage level is the output voltage.

22. The method according to claim 12 , further comprising:

providing the leakage compensation circuit for generating the leakage compensation current,

wherein the leakage compensation current comprises a current mirror and a biased transistor device coupled in series with one of the transistor devices of the current mirror.