Pseudo-differential active RC integrator

1. A pseudo-differential active RC integrator with common-mode feedback, comprising:

a first branch configured to receive a first component of a differential input signal and produce a first component of a differential output signal, the first branch comprising:

a first resistor;

a first virtual ground node;

a first transistor including a first terminal configured to receive the first component of the differential input signal via the first resistor and including a second terminal configured to produce the first component of the differential output signal; and

a first transconductor coupled to the first virtual ground node;

a second branch configured to receive a second component of the differential input signal and produce a second component of the differential output signal, the second branch comprising:

a second resistor;

a second virtual ground node;

a second transistor including a first terminal configured to receive the second component of the differential input signal via the second resistor and including a second terminal configured to produce the second component of the differential output signal; and

a second transconductor coupled to the second virtual ground node; and

a common-mode feedback subcircuit coupled to the first transconductor and the second transconductor and configured to adjust a common-mode output signal of the pseudo-differential active RC integrator.

2. The pseudo-differential active RC integrator of claim 1 , wherein the first terminal of the first transistor defines the first virtual ground node; and wherein the first terminal of the second transistor defines the second virtual ground node.

3. The pseudo-differential active RC integrator of claim 1 , wherein the common-mode feedback subcircuit comprises a gain stage having an input configured to receive the common-mode output signal, and an output coupled to the first transconductor and the second transconductor.

4. The pseudo-differential active RC integrator of claim 3 , wherein the gain stage comprises an operational amplifier.

5. The pseudo-differential active RC integrator of claim 3 , wherein the gain stage comprises an integrator.

6. The pseudo-differential active RC integrator of claim 3 , wherein the first transconductor comprises a third transistor and wherein the output of the gain stage is coupled to a gate terminal of the third transistor.

7. The pseudo-differential active RC integrator of claim 6 , wherein the second transconductor comprises a fourth transistor and wherein the output of the gain stage is coupled to a gate terminal of the fourth transistor.

8. The pseudo-differential active RC integrator of claim 3 , wherein the input of the gain stage is a first input, and wherein the gain stage further has a second input configured to receive a reference signal corresponding to a target value of the common-mode output signal.

9. The pseudo-differential active RC integrator of claim 3 , wherein the common-mode feedback subcircuit further comprises a capacitor in parallel with the gain stage.

10. The pseudo-differential active RC integrator of claim 2 , wherein the first terminal of the first transistor defining a first virtual ground node is a gate terminal.

11. The pseudo-differential active RC integrator of claim 3 , wherein the gain stage input configured to receive the common-mode output signal is coupled to the second terminal of the first transistor by a third resistor and is coupled to the second terminal of the second transistor by a fourth resistor; and

wherein the third resistor and the fourth resistor have approximately equal resistances.

12. The pseudo-differential active RC integrator of claim 11 , further comprising a first capacitor in parallel with the third resistor and a second capacitor in parallel with the fourth resistor.

13. A pseudo-differential active RC integrator with common-mode feedback, comprising:

a first branch configured to receive a first component of a differential input signal and produce a first component of a differential output signal at a first output node, the first branch including:

a first virtual ground node; and

a first transconductor coupled to the first virtual ground node;

a second branch configured to receive a second component of the differential input signal and produce a second component of the differential output signal at a second output node, the second branch including:

a second virtual ground node; and

a second transconductor coupled to the second virtual ground node; and

a common-mode feedback subcircuit with an output coupled to the first transconductor and the second transconductor and configured to adjust a common-mode output signal of the pseudo-differential active RC integrator, wherein the common-mode feedback subcircuit includes a reference voltage input and a second input connected to the first output node via a first resistor, the first resistor having a first capacitor connected in parallel, wherein the second input is further connected to the second output node via a second resistor, the second resistor having a second capacitor connected in parallel.

14. the pseudo-differential active RC integrator of claim 13 , wherein the common-mode feedback subcircuit includes an operational amplifier (opamp).

15. the pseudo-differential active RC integrator of claim 14 , wherein the common-mode feedback subcircuit includes only one opamp.

16. The pseudo-differential active RC integrator of claim 13 , wherein the first branch further includes:

a first transistor comprising:

a first terminal defining the first virtual ground node; and

a second terminal configured to produce the first component of the differential output signal; and

wherein the second branch further includes:

a second transistor including:

a first terminal defining the second virtual ground node; and

a second terminal configured to produce the second component of the differential output signal.

17. The pseudo-differential active RC integrator of claim 16 , wherein the second terminal of the first transistor is connected to a first current source, and wherein the second terminal of the second transistor is connected to a second current source.

18. The pseudo-differential active RC integrator of claim 17 , wherein the first virtual ground node is configured to have a substantially constant voltage having a value sufficient to keep a current through the first transistor substantially equal to the first current source, and wherein the second virtual ground node is configured to have a substantially constant voltage having a value sufficient to keep a current through the second transistor substantially equal to the second current source.