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:
Nov. 14, 1978
Filed:
Jun. 09, 1977
Richard J Cubbison, Jr, Littleton, CO (US);
Bell Telephone Laboratories, Incorporated, Murray Hill, NJ (US);
Abstract
A sample and hold circuit is disclosed which employs a matched pair of operational amplifiers as a decoupling circuit to isolate the output of the sample and hold circuit from the sampling capacitor. Prior art decoupling circuits employ a simple isolation amplifier which has a tendency to charge the sampling capacitor with the isolation amplifier input bias and leakage currents. The disclosed decoupling circuit employs one of a pair of matched operational amplifiers as a self-compensating isolation amplifier which dynamically generates the bias and leakage currents found at its input while isolating the sample and hold output from the sampling capacitor. The other operational amplifier is connected in series between the isolation amplifier and the sample and hold output and functions to cancel the input bias current signal generated by the self-compensating isolation amplifier. Thus, the net quiescent current into the input of the decoupling circuit is essentially zero, thereby eliminating the capacitor charging problem of prior art isolation amplifiers.