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:
Feb. 21, 1989
Filed:
Feb. 17, 1988
Michel S Michail, Wappingers Falls, NY (US);
James L Walsh, Hyde Park, NY (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
A half current switch comprising: at least one input transistor, a load resistance connected between a first voltage reference and the collector of the input transistor, a constant-current resistance connected between the emitter of the input transistor and a second voltage reference, and a feedback means including at least one feedback connected to the constant-current resistance. The feedback means further includes means for biasing the feedback transistor to drive a current through the constant current resistance which, when flowing, increases with an increasing main current and decreases with a decreasing main current through the input transistor. The feedback means thus causes a constant current to be drawn by the input transistor when it is conducting, thereby controlling the capacitance of the input transistor while maintaining the output level constant. In a preferred embodiment, the feedback means comprises a PNP transistor with its base connected to the collector of the input transistor, with its emitter connected to the first voltage reference, and with its collector connected to the emitter of the input transistor. The PNP transistor not only acts as a feedback device to control current, but also acts to prevent oscillations when a speed-up capacitor is used in the circuit.