Claims
- 1. 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.
- 2. The circuit of claim 1, wherein the scaling circuit comprises a voltage divider.
- 3. The circuit of claim 2, wherein the voltage divider applies a first voltage division factor to the first output and a second voltage division to the second output.
- 4. The circuit of claim 3, wherein the first and second division factors are approximately equal.
- 5. The circuit of claim 1, 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.
- 6. The circuit of claim 1, 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.
- 7. The circuit of claim 6, wherein the first and second gain factors are approximately equal.
CROSS REFERENCE TO RELATED DOCUMENTS
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.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
5521771 |
Keithley |
May 1996 |
|
5805022 |
Bruccoleri et al. |
Sep 1998 |
|