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:
Dec. 21, 1999
Filed:
Jul. 30, 1998
Robert Russell Hale, Beaverton, OR (US);
Credence Systems Corporation, Fremont, CA (US);
Abstract
When turned on by an input CONTROL signal, a MOSFET transistor switch in accordance with the present invention connects a low impedance voltage source to a moderate to high impedance load. The switch includes a relatively large first MOSFET transistor (Q1), a smaller second MOSFET transistor (Q2), a resistor and a current source. Source terminals of transistors Q1 and Q2 are tied to the voltage source. The load is connected to the drain of Q1 while the current source is connected to the drain of the Q2 and also to the gates of both transistors Q1 and Q2. The resistor links the gates of transistors Q1 and Q2 to the voltage source. When the CONTROL signal is asserted, it turns on the current source, thereby quickly turning transistors Q1 and Q2 on to connect the voltage source to the load. When the control source is de-asserted, the current source turns off. Transistors Q1 and Q2 then turn off at a controlled rate in order to minimize current injection into the load.