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. 24, 2009
Filed:
Mar. 06, 2006
Chau C. Tran, Malden, MA (US);
A. Paul Brokaw, Tucson, AZ (US);
Chau C. Tran, Malden, MA (US);
A. Paul Brokaw, Tucson, AZ (US);
Analog Devices, Inc., Norwood, MA (US);
Abstract
A temperature setpoint circuit comprises bipolar transistors Qand Qwhich receive currents Iand Iat their respective collectors and are operated at unequal current densities, with a resistance Rconnected between their bases such that the difference in their base-emitter voltages (ΔV) appears across R. An additional PTAT current Iis maintained in a constant ratio to Iand Iand provided to the collector of Qwhile Qis off, and is not provided while Qis on. The circuit is arranged such that Qis turned on and conducts a current equal to Ia when: ΔV=(kT/q)ln(NI/Ia), where Ia=I+I, the temperature T at which ΔV=(kT/q)ln(NI/Ia) being the circuit's setpoint temperature, such that the switching of current Iprovides hysteresis for the setpoint temperature which is approximately constant over temperature.