Combined filter and transconductance amplifier

1. Circuitry comprising:

a passive circuit adapted to receive an input signal; and

an operational transconductance amplifier (OTA) coupled to the passive circuit and adapted to provide an output current, such that:

the passive circuit and the OTA provide a high-pass filter, which is configured to high-pass filter and integrate the input signal to provide the output current;

the passive circuit comprises a feedback impedance circuit coupled between an output from the OTA and an inverting input to the OTA; and

during a first set of operating conditions, the feedback impedance circuit has a feedback current, such that a magnitude of the output current is at least ten times greater than a magnitude of the feedback current.

2. The circuitry of claim 1 wherein the passive circuit does not comprise any active elements.

3. The circuitry of claim 1 wherein the OTA is a single OTA.

4. The circuitry of claim 1 wherein a cutoff frequency of the high-pass filter is greater than about one megahertz.

5. The circuitry of claim 1 wherein a cutoff frequency of the high-pass filter is equal to about six megahertz.

6. The circuitry of claim 1 wherein the high-pass filter is a two-pole filter.

7. The circuitry of claim 1 wherein the passive circuit comprises a low-pass filter, such that the output current is further based on low-pass filtering the input signal.

8. Circuitry comprising:

a passive circuit adapted to receive an input signal; and

an operational transconductance amplifier (OTA) coupled to the passive circuit and adapted to provide an output current, such that:

the passive circuit and the OTA provide a high-pass filter, which is configured to high-pass filter and integrate the input signal to provide the output current;

the passive circuit comprises a low-pass filter, such that the output current is further based on low-pass filtering the input signal; and

a cutoff frequency of the high-pass filter is about equal to a cutoff frequency of the low-pass filter.

9. The circuitry of claim 1 wherein:

the passive circuit further comprises a shunt impedance circuit coupled between a non-inverting input to the OTA and a ground;

during the first set of operating conditions, the feedback impedance circuit has a feedback impedance and the shunt impedance circuit has a shunt impedance; and

the feedback impedance is about equal to the shunt impedance.

10. The circuitry of claim 1 wherein the passive circuit further comprises a negative-side impedance circuit coupled between the inverting input to the OTA and an input, which is adapted to receive the input signal.

11. The circuitry of claim 1 wherein the OTA is further adapted to provide a derived output current that is representative of the output current.

12. The circuitry of claim 11 wherein a magnitude of the derived output current is programmable.

13. The circuitry of claim 11 wherein the OTA is further adapted to provide a current sense signal that is representative of the derived output current.

14. Circuitry comprising:

an active ripple cancellation circuit and a switching supply inductive element;

a passive circuit adapted to receive an input signal; and

an operational transconductance amplifier (OTA) coupled to the passive circuit and adapted to provide an output current, such that:

the passive circuit and the OTA high-pass filter and integrate the input signal to provide the output current;

the OTA and the passive circuit provide a combined filter and OTA;

the OTA is further adapted to provide a derived output current that is representative of the output current;

the active ripple cancellation circuit comprises the combined filter and OTA;

the switching supply inductive element has an inductor current having a ripple current; and

the derived output current at least partially cancels the ripple current.

15. The circuitry of claim 14 further comprising a radio frequency (RF) power amplifier (PA) wherein:

the RF PA is adapted to receive and amplify an RF input signal to provide an RF transmit signal using an envelope power supply signal; and

the envelope power supply signal is at least partially based on the inductor current.

16. The circuitry of claim 14 further comprising switching circuitry wherein:

the switching circuitry is adapted to provide an inductor input signal to the switching supply inductive element and the active ripple cancellation circuit; and

the derived output current is based on the inductor input signal.

17. The circuitry of claim 16 wherein:

the active ripple cancellation circuit further comprises a delay circuit coupled between the switching circuitry and the combined filter and OTA;

the delay circuit is adapted to receive the inductor input signal; and

the delay circuit is further adapted to provide the input signal based on delaying the inductor input signal.