Amplifier capacitive load compensation

1. An amplifier, comprising:

a first stage including:

an output;

a first compensation network coupled to the output of the first stage;

a second stage including:

a source follower including:

an input coupled to the output of the first stage; and

an output; and

a second compensation network coupled between the input of the source follower and the output of the source follower;

wherein:

the source follower includes a first transistor having:

a first current terminal coupled to a power supply terminal;

a second current terminal coupled to the second compensation network; and

a control terminal coupled to the output of the first stage; and

the second stage includes:

a second transistor including:

a first current terminal coupled to the first current terminal of the first transistor;

a control terminal coupled to the control terminal of the first transistor; and

a second current terminal; and

a current mirror circuit coupled to the second current terminal of the first transistor and the second current terminal of the second transistor, wherein the current mirror circuit includes:

a third transistor including:

a first current terminal coupled to the second current terminal of the first transistor;

a second current terminal coupled to ground; and

a control terminal; and

a fourth transistor including:

a first current terminal coupled to the second current terminal of the second transistor;

a control terminal coupled to the control terminal of the third transistor; and

a second current terminal coupled to the control terminal of the third transistor.

2. The amplifier of claim 1 , wherein the second compensation network includes:

a resistor including:

a first terminal coupled to the control terminal of the first transistor; and

a second terminal coupled to the second current terminal of the first transistor.

3. The amplifier of claim 2 , wherein the second compensation network includes:

a capacitor including:

a first terminal coupled to the second terminal of the resistor; and

a second terminal coupled to the second current terminal of the first transistor.

4. The amplifier of claim 1 , wherein the source follower includes a current source coupled between the output of the source follower and ground.

5. The amplifier of claim 1 , wherein the first compensation network includes:

a resistor including:

a first terminal coupled to the output of the first stage; and

a second terminal; and

a capacitor including:

a first terminal coupled to the second terminal of the resistor; and

a second terminal coupled to ground.

6. An amplifier, comprising:

a first stage configured to amplify a received signal; and

a second stage coupled to the first stage, and including:

a source follower including an input and an output; and

a compensation network between the input and the output, and configured to modify a magnitude and phase response of the first stage based on a load capacitance coupled to the output of the source follower;

wherein:

the source follower includes a first transistor including:

a first current terminal coupled to a power supply terminal;

a second current terminal coupled to ground; and

a control terminal coupled to the first stage; and

the second stage includes a second transistor having:

a first current terminal coupled to the power supply terminal;

a second current terminal coupled to ground; and

a control terminal coupled to the control terminal of the first transistor.

7. The amplifier of claim 6 , wherein the compensation network includes a capacitor coupled between the input of the source follower and the output of the source follower.

8. The amplifier of claim 7 , wherein:

the compensation network includes a resistor coupled between the input of the source follower and the output of the source follower; and

the resistor is coupled in series with the capacitor.

9. The amplifier of claim 6 , wherein the source follower includes a current source coupled between the output of the source follower and ground.

10. The amplifier of claim 9 , wherein the second stage includes:

a current mirror circuit having:

a third transistor coupled between the first transistor and ground; and

a fourth transistor coupled between the second transistor and ground.

11. A DC-DC converter comprising:

a controller;

a power stage coupled to the controller, and including:

an amplifier having:

a first stage configured to amplify a received signal; and

a second stage coupled to the first stage, and including:

a source follower, wherein the source follower includes:

an input and an output; and

a first transistor including:

a first current terminal coupled to a power supply terminal;

a second current terminal coupled to ground; and

a control terminal coupled to the first stage;

a compensation network coupled between the input and the output, and configured to modify a magnitude and phase response of the first stage based on a load capacitance coupled to the output of the source follower; and

a second transistor including:

a first current terminal coupled to the power supply terminal;

a second current terminal coupled to ground; and

a control terminal coupled to the control terminal of the first transistor.

12. The DC-DC converter of claim 11 , wherein the compensation network includes a capacitor and a resistor coupled in series between the input of the source follower and the output of the source follower.

13. The amplifier of claim 11 , wherein the second stage includes:

a current mirror circuit having:

a third transistor coupled between the first transistor and ground; and

a second transistor coupled between the second transistor and ground.