The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 26, 1991
Filed:
Jan. 03, 1990
John E Hanna, Mesa, AZ (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
A filter cell having common mode compensation for use in a differential integrating filter includes a transconductance amplifier that comprises a pair of differentially connected transistors the bases of which are coupled to respective inputs of the filter cell and whose emitters are interconnected to a current sinking transistor while the collectors are coupled via respective output circuitry to first and second outputs of the filter cell. Circuitry is provided to set the common voltage levels at the first and second outputs of the comprising a pair of resistors commonly connected at a circuit node that is a virtual ground for differential signals and the first and second filter cell outputs respectively. The circuit node is also coupled to the base of the current sinking transistor to thereby for a common mode closed loop in conjunction with a current supply that is also coupled to the circuit node. Common mode compensation to inhibit loop instability is provided by a pair of capacitors coupled in series between the collectors of differentially connected transistors and having the junction therebetween connected to the base of the current sinking transistor.