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:
Jun. 28, 1994
Filed:
Jan. 25, 1993
Michael McGinn, Scottsdale, AZ (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
An active filter circuit (10) that has a cut off frequency being substantially independent of absolute and temperature variations due to on chip resistors (R.sub.1, R.sub.2 and R.sub.3) has been provided. The active filter includes a transconductance gain amplifier (16) having first and second currents (I.sub.B and I.sub.E) the ratio of which are controlled such that the absolute and temperature effects of any on chip resistors of the active filter circuit are removed. The ratio of the first and second currents of the transconductance gain amplifier are controlled by a circuit that generates third and fourth currents (I.sub.b and I.sub.e) which are a function of a bandgap voltage. The circuit then utilizes the third and fourth currents and provides, to the transconductance gain amplifier, a current that is substantially equal to the ratio of square of the third current to the fourth current, and a current substantially equal to the fourth current.