Patent Number: 6,297,698

Title: Circuit for automatic regulation of a differential amplifier's gain

Abstract: A circuit for regulating the gain of a variable differential gain amplifier. In one embodiment, a fully differential amplifier amplifies the outputs of the variable gain amplifier. The outputs of the fully differential amplifier are applied to a three input comparator so that if either of the outputs are greater than a reference voltage, a control signal is generated which is used to regulate the gain of the variable gain amplifier. In other embodiments, an analog OR function is used as an input to a conventional two input comparator in place of the three input comparator. In another embodiment, outputs of the variable gain amplifier are passed through switches to a scaling circuit which either voltage divides or amplifies and combines the outputs before application to a comparator. In each case, known asymmetries can be compensated for by independent gain control of each of the outputs of the variable gain differential amplifier.

Inventors: Callahan, Jr.; Michael J. (Austin, TX)

Assignee: STMicroelectronics, Inc.

International Classification: H03G 3/20 (20060101); H03F 3/45 (20060101); H03F 003/45 ()

Expiration Date: 10/02/2018