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. 28, 1996
Filed:
Mar. 15, 1994
James R Ohannes, Portland, ME (US);
Stephen W Clukey, South Portland, ME (US);
E David Haacke, Westbrook, ME (US);
Roy L Yarbrough, Hiram, ME (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
An enhanced bipolar-transistor apparatus for protecting electronic devices from electrostatic discharge damage. The apparatus is built around a bipolar transistor coupled between a power rail and the circuit to be protected. The protection is based on the high-current-capacity path through the bipolar transistor which is opened up either by collector-to-emitter punch-through in the bipolar transistor or by the bipolar transistor going into normal conduction upon being turned on by a switch coupled to the base of the bipolar transistor. In the preferred embodiment the switch is a MOS transistor that is designed to undergo source-to-drain breakdown at a fixed threshold voltage, whereupon it activates the bipolar transistor which in turn discharges the overvoltage. In this way the advantages of the high-current-capacity bipolar transistor are obtained without the concern that fabrication vagaries will prevent the bipolar transistor from providing needed protection, such as is the situation where the punch-through phenomenon alone is relied on.