Claims
- 1. A circuit which regulates gain in a differential amplifier having first and second outputs, comprising:
a fully differential amplifier receiving the first and second outputs, said fully differential amplifier producing first and second amplified outputs; a comparison circuit which compares the first and second amplified outputs with a reference and produces an output signal if either the first or second amplified output exceeds the reference; and a processing circuit, connected to receive the output signal from the comparison circuit, to generate a regulating signal dependent upon a duration of the output signal wherein the regulating signal regulates a gain of the differential amplifier.
- 2. The circuit of claim 1, wherein the fully differential amplifier has a first gain applied to the first output of the differential amplifier and a second gain applied to the second output of the differential amplifier to produce amplified first and second outputs.
- 3. The circuit of claim 2, wherein the first and second gains are equal.
- 4. The circuit of claim 1, wherein the comparison circuit comprises a three input comparator having two inputs which are compared with a reference input.
- 5. The circuit of claim 4, wherein the two inputs are inverting inputs and the reference input is a non-inverting input.
- 6. The circuit of claim 4, wherein the two inputs are non-inverting inputs and the reference input is an inverting input.
- 7. The circuit of claim 1, wherein the processing circuit comprises:
a charge pump receiving the output signal from the comparison circuit and producing a control voltage; and a voltage to current converter receiving the control voltage from the charge pump and producing a control current therefrom, the control current operating as the regulating signal.
- 8. The circuit of claim 1, wherein the comparison circuit comprises a comparator having a single input which is compared with a reference and further comprising an analog OR circuit receiving the first and second outputs and producing an output to the single input of the comparator.
- 9. The circuit of claim 8, wherein the analog OR circuit is comprised of two source followers having inputs at their respective gates and sharing a common current source at their respective sources, with the output being taken at a junction of the current source and the respective sources.
- 10. A circuit which regulates gain in a differential amplifier having first and second outputs, comprising:
a first switch coupled to the first output, the first switch being controlled by the second output; a second switch coupled to the second output, the second switch being controlled by the first output; a scaling circuit receiving the first and second outputs under control of the first and second switches to produce a scaled output; a comparison circuit which compares the scaled output with a reference and produces an output signal if the scaled output exceeds the reference; and a processing circuit, connected to receive the output signal from the comparison circuit, to generate a regulating signal dependent upon a duration of the output signal wherein the regulating signal regulates the gain of the differential amplifier.
- 11. The circuit of claim 10, wherein the scaling circuit comprises a voltage divider.
- 12. The circuit of claim 11, wherein the voltage divider applies a first voltage division factor to the first output and a second voltage division to the second output.
- 13. The circuit of claim 12, wherein the first and second division factors are approximately equal.
- 14. The circuit of claim 10, wherein the scaling circuit comprises a summing amplifier receiving the first and second outputs, said summing amplifier producing first and second amplified outputs which are applied to the comparison circuit.
- 15. The circuit of claim 10, wherein the fully differential amplifier has a first gain factor applied to the first output and a second gain factor applied to the second output.
- 16. The circuit of claim 15, wherein the first and second gain factors are approximately equal.
- 17. A circuit which regulates gain in a differential amplifier having first and second outputs, comprising:
a fully differential amplifier receiving the first and second outputs, the fully differential amplifier having a first gain applied to the first output and a second gain applied to the second output to produce first and second amplified outputs; a comparison circuit which compares the amplified first and second amplified outputs with a reference and produces an output signal if either the first or second amplified output exceeds the reference, and wherein the comparison circuit comprises a comparator having multiple inputs which are compared with a reference; and a processing circuit, connected to receive the output signal from the comparison circuit, to generate a regulating signal dependent upon a duration of the output signal, the processing circuit comprising:
a charge pump receiving the output signal from the comparison circuit and producing a control voltage; and a voltage to current converter receiving the control voltage from the charge pump and producing a control current therefrom, the control current operating as a regulating signal which regulates the gain of the differential amplifier.
- 18. A method of regulating a gain of a variable gain differential amplifier having output signals, comprising:
amplifying the output signals to produce amplified signals; comparing the amplified signals with a reference in a comparison circuit; and if either amplified signal exceeds the threshold, generating a regulating signal to reduce the gain of the variable gain amplifier.
- 19. The method of claim 18, wherein the amplifying is carried out in a fully differential amplifier.
- 20. The method of claim 19, wherein the fully differential amplifier has a first gain factor applied to the first output and a second gain factor applied to the second output.
- 21. The method of claim 18, wherein the comparison circuit comprises a three input comparator.
- 22. The method of claim 18 wherein the regulating signal has a duration depending upon the output signals.
- 23. The method of claim 18, wherein the amplifying is carried out in an amplifier having gain greater than 1.
- 24. A method of detecting a level of a differential output signal, comprising:
comparing each differential output signal with a reference signal using a single comparison circuit; and if either output signal exceeds the reference signal, generating an output signal.
- 25. The method of claim 24, wherein the comparing is carried out in a three input comparator.
- 26. The method of claim 24, wherein the comparing is carried out in a comparison circuit comprising a comparator having a single input which is compared with a reference and an analog OR circuit receiving the differential output signals and producing an output to the single input of the comparator.
CROSS REFERENCE TO RELATED DOCUMENTS
[0001] U.S. Pat. No. 5,805,022 to Bruccoleri et al. and U.S. Pat. No. 5,349,304 to Ryat are hereby incorporated by reference.
Divisions (1)
|
Number |
Date |
Country |
Parent |
09561093 |
Apr 2000 |
US |
Child |
09963023 |
Sep 2001 |
US |