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:
Jul. 31, 1979
Filed:
May. 30, 1978
Daniel D Culmer, Sunnyvale, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A system for establishing a precise reference current and steering the precise reference current through a load. A reference resistance is connected between a first node and a common terminal and a first reference voltage is maintained at the first node to establish a precise current flow through the reference resistance. A capacitance is connected between the source and the gate of a field effect transistor. A first switch is provided for connecting the field effect transistor in series with the reference resistance. A control loop is connected to a second node in the series circuit between the first switch and the field effect transistor and to a second reference voltage terminal. A second switch is provided for connecting the control loop to the gate of the field effect transistor; and a third switch connected to the second node is provided for connecting the field effect transistor in series with a load. When the first and second switches are closed and the third switch is open, the control loop causes the capacitance to be charged until the voltage at the second node matches the second reference voltage to thereby provide a voltage across the gate and source of the field effect transistor for sustaining the flow of the precise current through the reference resistor. When the first and second switches are opened and the third switch is closed, the charge on the capacitance causes the precise current to continue to flow from the field effect transistor and the third switch steers the current through the load.