Restoring output common-mode of amplifier via capacitive coupling

• US 8,633,764 B2
• Filed: 06/10/2011
• Issued: 01/21/2014
• Est. Priority Date: 06/10/2011
• Status: Expired due to Fees

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Agrawal, Ankur, Bulzacchelli, John F., Toifl, Thomas H.
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US13/157,957
• Publication Number:
  US 20120313703A1
• Time in Patent Office: 956 Days
• Field of Search: 330/11, 330/258, 327/336
• US Class Current: 330/11
• CPC Class Codes: H03F 2200/264 An operational amplifier based integrator or transistor based integrator being used in an amplifying circuit
• CPC Class Codes: H03F 2203/45681 the LC comprising offset compensating means
• CPC Class Codes: H03F 3/211 using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence
• CPC Class Codes: H03F 3/45197 Pl types H03F3/45224, H03F3/45251 take precedence
• CPC Class Codes: H03F 3/45632 in differential amplifiers with FET transistors as the active amplifying circuit H03F3/4578 takes precedence

Abstract

An apparatus comprises an amplifier circuit comprising at least one output node and a common-mode restoration circuit capacitively coupled to the at least one output node of the amplifier circuit. The common-mode restoration circuit is configured to introduce at least one common-mode restoring signal onto the output node, wherein the at least one common-mode restoring signal transitions in correspondence with an operation interval of the amplifier circuit and thereby compensates for a common-mode voltage drop on the at least one output node of the amplifier circuit. In one example, the amplifier circuit may comprise a current-integrating amplifier circuit, and the operation interval may comprise an integration interval.

Claims

1. An apparatus, comprising:

an amplifier circuit comprising at least one output node; and

a common-mode restoration circuit capacitively coupled to the at least one output node of the amplifier circuit and configured to generate and apply at least one common-mode restoring signal onto the output node via the capacitive coupling, wherein the at least one common-mode restoring signal transitions in correspondence with an operation interval of the amplifier circuit and thereby compensates for a common-mode voltage drop on the at least one output node of the amplifier circuit, and wherein the common-mode restoration circuit generates the at least one common-mode restoring signal without an analog input signal applied to the common-mode restoration circuit.

2. The apparatus of claim 1, wherein the amplifier circuit comprises a current-integrating amplifier circuit, and the operation interval comprises an integration interval.

5. The apparatus of claim 2, wherein the current-integrating amplifier circuit comprises a differential amplifier with two output nodes such that the common-mode restoration circuit introduces two common-mode restoring signals onto the two output nodes, respectively.

6. The apparatus of claim 5, wherein the common-mode restoration circuit comprises a single current-starved inverter to generate the two common-mode restoring signals.

7. The apparatus of claim 5, wherein the common-mode restoration circuit comprises two current-starved inverters to generate the two common-mode restoring signals, respectively.

8. The apparatus of claim 5, wherein the common-mode restoration circuit comprises at least one differential current switch, wherein the at least one differential current switch represents at least one feedback tap of a decision feedback equalizer summer circuit.

9. The apparatus of claim 5, wherein the common-mode restoration circuit comprises two simple gating logic circuits to generate the two common-mode restoring signals, respectively.

10. The apparatus of claim 2, wherein the current-integrating amplifier circuit comprises a multi-input amplifier that sums multiple input signals to implement one of a decision feedback equalizer summer circuit and a feed-forward equalizer summer circuit.

3. The apparatus of 2, wherein the transition of the common-mode restoring signal is complementary to the common-mode voltage drop on the at least one output node during the integration interval of the current-integrating amplifier circuit.

4. The apparatus of claim 3, wherein the transition of the common-mode restoring signal comprises one of a rising edge transition and a falling edge transition.

11. A method, comprising:

applying at least one common-mode restoring signal onto at least one output node of an amplifier circuit capacitively coupled to a common-mode restoration circuit, wherein the at least one common-mode restoring signal is generated by the common-mode restoration circuit without an analog input signal applied to the common-mode restoration circuit, and applied to the output node via the capacitive coupling, and wherein the at least one common-mode restoring signal transitions in correspondence with an operation interval of the amplifier circuit and thereby compensates for a common-mode voltage drop on the at least one output node of the amplifier circuit.

12. The method of claim 11, wherein the amplifier circuit comprises a current-integrating amplifier circuit, and the operation interval comprises an integration interval.

15. The method of claim 12, wherein the current-integrating amplifier circuit comprises a differential amplifier with two output nodes such that the common-mode restoration circuit introduces two common-mode restoring signals onto the two output nodes, respectively.

16. The method of claim 15, wherein the common-mode restoration circuit comprises a single current-starved inverter to generate the two common-mode restoring signals.

17. The method of claim 15, wherein the common-mode restoration circuit comprises two current-starved inverters to generate the two common-mode restoring signals, respectively.

18. The method of claim 15, wherein the common-mode restoration circuit comprises at least one differential current switch, wherein the at least one differential current switch represents at least one feedback tap of a decision feedback equalizer summer circuit.

19. The method of claim 15, wherein the common-mode restoration circuit comprises two simple gating logic circuits to generate the two common-mode restoring signals, respectively.

20. The method of claim 12, wherein the current-integrating amplifier circuit comprises a multi-input amplifier that sums multiple input signals to implement one of a decision feedback equalizer summer circuit and a feed-forward equalizer summer circuit.

13. The method of 12, wherein the transition of the common-mode restoring signal is complementary to the common-mode voltage drop on the at least one output node during the integration interval of the current-integrating amplifier circuit.

14. The method of claim 13, wherein the transition of the common-mode restoring signal comprises one of a rising edge transition and a falling edge transition.

21. One or more integrated circuits, comprising:

an amplifier circuit portion of the one or more integrated circuits comprising at least one output node; and

a common-mode restoration circuit portion of the one or more integrated circuits capacitively coupled to the at least one output node of the amplifier circuit portion and configured to generate and apply at least one common-mode restoring signal onto the output node via the capacitive coupling, wherein the at least one common-mode restoring signal transitions in correspondence with an operation interval of the amplifier circuit portion and thereby compensates for a common-mode voltage drop on the at least one output node of the amplifier circuit portion, and wherein the common-mode restoration circuit portion generates the at least one common-mode restoring signal without an analog input signal applied to the common-mode restoration circuit portion.

22. The one or more integrated circuits of claim 21, wherein the amplifier circuit portion comprises a current-integrating amplifier circuit portion, and the operation interval comprises an integration interval.

23. The one or more integrated circuits of 22, wherein the transition of the common-mode restoring signal is complementary to the common-mode voltage drop on the at least one output node during the integration interval of the current-integrating amplifier circuit portion.