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:
Sep. 01, 1987
Filed:
Apr. 29, 1985
Arthur H Van Roermund, Eindhoven, NL;
Petrus M Coppelmans, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
A first resistor (R.sub.1) and a first capacitor (C.sub.1) constitute a filter arrangement having a time constant which is not very accurate due to the inaccuracy of the resistor and the capacitor values in integrated circuits. The time constant is adjusted using a circuit comprising a reference resistor (R.sub.2) and a switched capacitor (C.sub.3). The value of the reference resistor (R.sub.2) and the equivalent resistance of the switched capacitor (C.sub.3) are compared by means of an integrator (C.sub.2, 2) from whose output (9) a control voltage is taken via a hold circuit (C.sub.4, C.sub.5). The control voltage is equal to the voltage at that point on the reference resistor where the resistance value is equal to that of the switched capacitor (C.sub.3). By means of comparators (21 to 30) and switches (S.sub.11 to S.sub.20) a percentage of the total resitance of the first resistor (R.sub.1) is short-circuited. This percentage is equal to the difference between the resistance of the reference resistor (R.sub.2) and the equivalent resistance of the switched capacitor (C.sub.3), expressed as a percentage of this equivalent resistance.