Low dropout regulator with resistive device

1 . A low dropout regulator for providing an output voltage, the low dropout regulator comprising:

a resistive device configured to contribute to stability of the low dropout regulator during operation and to have a resistance that is dependent on a load current;

a first resistive element;

a second resistive element;

a first amplifier;

a regulator transistor; and

a first capacitor,

wherein:

the first resistive element and the second resistive element are coupled in series;

the regulator transistor and the first resistive element are coupled at an output node for providing the output voltage;

the first resistive element and the second resistive element are coupled at a feedback node for providing a feedback voltage, the feedback node being coupled to a second input terminal of the first amplifier;

the regulator transistor is coupled to a first voltage terminal;

the second resistive element is coupled to a second voltage terminal;

the resistive device is directly coupled to the output node, an output terminal of the first amplifier and the first voltage terminal;

the regulator transistor is directly coupled to the output terminal of the first amplifier;

the first capacitor is directly coupled to the second input terminal; and

the resistive device further comprises:

a first negative threshold transistor;

a first transistor coupled in series with the first negative threshold transistor; and

a second transistor coupled in series with a second negative threshold transistor, the series coupling of the first negative threshold transistor and the first transistor being coupled in parallel with the series coupling of the second negative threshold transistor and the second transistor.

2 . The low dropout regulator of claim 1 wherein the first amplifier comprises:

i) a first input terminal for receiving a reference voltage;

ii) the second input terminal for receiving the feedback voltage; and

iii) the output terminal; and

wherein the regulator transistor comprises a gate terminal coupled to the output terminal of the first amplifier.

3 . The low dropout regulator of claim 1 , wherein the first capacitor is configured to contribute to the stability of the low dropout regulator during operation.

4 . The low dropout regulator of claim 3 , wherein the first capacitor is configured to contribute to the stability of the low dropout regulator during operation by cancelling a pole at the second input terminal of the first amplifier.

5 . The low dropout regulator of claim 1 further comprising a load device coupled to the output node, the load current being provided across the load device during operation.

6 . The low dropout regulator of claim 5 , wherein the load device comprises a first terminal coupled to the output node and a second terminal coupled to the second voltage terminal.

7 . The low dropout regulator of claim 1 , wherein the first negative threshold transistor comprises a first terminal coupled to the output node and a second terminal coupled to a first terminal of the first transistor.

8 . The low dropout regulator of claim 7 , wherein the first transistor comprises a second terminal coupled to a first voltage terminal and a gate terminal coupled to the output terminal of the first amplifier.

9 . A low dropout regulator for providing an output voltage, the low dropout regulator comprising:

a resistive device configured to contribute to stability of the low dropout regulator during operation and to have a resistance that is dependent on a load current;

a first resistive element;

a second resistive element;

a first amplifier;

a regulator transistor; and

a first capacitor,

wherein:

the first resistive element and the second resistive element are coupled in series;

the regulator transistor and the first resistive element are coupled at an output node for providing the output voltage;

the first resistive element and the second resistive element are coupled at a feedback node for providing a feedback voltage, the feedback node being coupled to a second input terminal of the first amplifier;

the regulator transistor is coupled to a first voltage terminal;

the second resistive element is coupled to a second voltage terminal;

the resistive device is directly coupled to the output node, an output terminal of the first amplifier and the first voltage terminal;

the regulator transistor is directly coupled to the output terminal of the first amplifier;

the first capacitor is directly coupled to the second input terminal;

the first amplifier comprises:

i) a first input terminal for receiving a reference voltage;

ii) the second input terminal for receiving the feedback voltage; and

iii) the output terminal;

the regulator transistor comprises a gate terminal coupled to the output terminal of the first amplifier;

the resistive device comprises further a first negative threshold transistor;

the resistive device further comprises a first transistor coupled in series with the first negative threshold transistor;

the first negative threshold transistor comprises a first terminal coupled to the output node and a second terminal coupled to a first terminal of the first transistor;

the first transistor comprises a second terminal coupled to a first voltage terminal and a gate terminal coupled to the output terminal of the first amplifier; and

wherein the resistive device comprises a second transistor coupled in series with a second negative threshold transistor, the series coupling of the first negative threshold transistor and the first transistor being coupled in parallel with the series coupling of the second negative threshold transistor and the second transistor.

10 . The low dropout regulator of claim 9 , wherein the second negative threshold transistor comprises a first terminal coupled to the output node and a second terminal coupled to a first terminal of the second transistor.

11 . The low dropout regulator of claim 10 , wherein the second transistor comprises a second terminal coupled to the first voltage terminal and a gate terminal coupled to the output terminal of the first amplifier.

12 . The low dropout regulator of claim 11 , wherein the second terminal of the second negative threshold transistor is coupled to the first terminal of the second transistor via a third resistive element and/or the first terminal of the second transistor is coupled to the output node via a fourth resistive element.

13 . A method of providing an output voltage, comprising:

providing a low dropout regulator for providing an output voltage, wherein the low dropout regulator comprises:

a resistive device configured to contribute to stability of the low dropout regulator during operation and to have a resistance that is dependent on a load current;

a first resistive element;

a second resistive element;

a first amplifier;

a regulator transistor; and

a first capacitor,

wherein:

the first resistive element and the second resistive element are coupled in series;

the regulator transistor and the first resistive element are coupled at an output node for providing the output voltage;

the first resistive element and the second resistive element are coupled at a feedback node for providing a feedback voltage, the feedback node being coupled to a second input terminal of the first amplifier;

the regulator transistor is coupled to a first voltage terminal;

the second resistive element is coupled to a second voltage terminal;

the resistive device is directly coupled to the output node, an output terminal of the first amplifier and the first voltage terminal;

the resistive device comprises a first negative threshold transistor;

the regulator transistor is directly coupled to the output terminal of the first amplifier;

the first capacitor directly coupled to the second input terminal; and

the first capacitor is directly coupled to the first negative threshold transistor.

14 . The low dropout regulator of claim 1 , wherein the first capacitor is directly coupled between the second input terminal and the resistive device.