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, 1995
Filed:
Dec. 21, 1994
Jose J Aizpuru, Garland, TX (US);
Walter T Matzen, Richardson, TX (US);
Honeywell Inc., Minneapolis, MN (US);
Abstract
A phototransistor is provided with a first resistor that operates as a shunt and a second resistor that operates to protect the device from damage that could be caused by a reverse bias condition. The possible damage results from the creation of a PN junction relationship caused by the doping of N conductivity type material with P.sup.+ conductivity type material in order to form the first resistor. This junction relationship creates a parasitic diode that provides a current path between the emitter and collector terminals of the phototransistor. In order to prevent damage that might occur during a reverse voltage connection, a second resistor is connected between the emitter of transistor Q.sub.1 and the first resistor. The second resistor is in series with the junction relationship resulting from the structure used to form the first resistor and therefore serves to limit the current flowing between the emitter and collector terminals of the transistor under reversed bias conditions.