Combined filter and transconductance amplifier

• US 8,957,728 B2
• Filed: 10/09/2012
• Issued: 02/17/2015
• Est. Priority Date: 10/06/2011
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Gorisse, Philippe
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US13/647,815
• Publication Number:
  US 20130088291A1
• Time in Patent Office: 861 Days
• Field of Search: 330/136, 330/306, 330/302
• US Class Current: 330/136
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 1/0266 by using a signal derived from the input signal
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 2203/45526 the FBC comprising a resistor-capacitor combination and being coupled between the LC and the IC
• CPC Class Codes: H03F 2203/45548 the IC comprising one or more capacitors as shunts to earth or as short circuit between inputs
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H03F 3/45475 using IC blocks as the active amplifying circuit
• CPC Class Codes: H03H 11/0427 Filters using a single transconductance amplifier; Filters derived from a single transconductor filter, e.g. by element substitution, cascading, parallel connection H03H11/0433 - H03H11/0472 take precedence

Abstract

Embodiments of circuitry, which includes an operational transconductance amplifier and a passive circuit, are disclosed. The passive circuit is coupled to the operational transconductance amplifier. Further, the passive circuit receives an input signal and the operational transconductance amplifier provides an output current, such that the passive circuit and the OTA high-pass filter and integrate the input signal to provide the output signal.

Claims

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.

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.

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.

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.