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:
May. 11, 1999
Filed:
Jun. 02, 1997
William J Scheraga, Warwick, RI (US);
Cherry Semiconductor Corporation, East Greenwich, RI (US);
Abstract
A control circuit for providing fast turn-off of a PNP transistor with output transient protection. An embodiment of the invention provides a current amplifier coupled between a positive voltage supply line and the base of a PNP switching transistor and an input device for providing an input current to the current amplifier. The current amplifier provides a transitory reverse drive current to the base of the PNP switching transistor. The current amplifier and the input device both include transient blocking junctions that block current flow from a positive voltage transient in excess of the positive supply voltage. The current amplifier is a PNP drive transistor in the preferred embodiment. The PNP drive transistor provides a transitory reverse drive current to the base of the PNP switching transistor. Control of the PNP drive transistor can be provided by a capacitor coupled between an input node and the base of an NPN transistor, the collector of the NPN transistor providing an amplified capacitor current to the base of the PNP drive transistor. A switching signal on the input node intermittently switches on and off a current source which intermittently drives the PNP switching transistor.