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:
Mar. 28, 1978
Filed:
Dec. 10, 1975
Jan Lohstroh, Eindhoven, NL;
U.S. Philips Corporation, New York, NY (US);
Abstract
A device for reading out the charge condition of a phototransistor by means of sampling pulses, for example read out of a transistor to be selected from a matrix of phototransistors, a voltage which is a measure of said charge condition being taken from the emitter of the phototransistor. In order to avoid the storage effect owing to the time constant which depends on the differential resistance of the base-emitter-junction, the emitter circuit of the phototransistor includes a current source which at the instant of sampling is switched on, while furthermore the emitter voltage of the phototransistor is applied to a voltage comparator circuit which supplies a voltage for switching off the current source at the instant that said emitter voltage drops below a specified reference value. In the case of read-out after a dark period some charge is drained owing to the response time of electronic systems, which charge can be compensated for by simple injection means.