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:
Sep. 08, 1992
Filed:
Sep. 25, 1991
Fujitsu Limited, Kawasaki, JP;
Abstract
A constant current circuit having an output current I.sub.2 which changes with the change of the power source voltage V.sub.cc, and an oscillating circuit whose oscillation frequency is made variable by the change of I.sub.2 in the constant current circuit. The constant current circuit comprises bipolar transistors coupled to form a differential amplifier, wherein one of the transistors is supplied with a reference voltage and another is supplied with a divided voltage of V.sub.cc, and a resistor connecting the emitters of the transistors is provided for controlling the slope of the V.sub.cc -I.sub.2 characteristic curve of the constant current circuit. The oscillating circuit comprises a capacitor charged with I.sub.2 and a switching circuit for discharging the capacitor when it is closed and a voltage detecting circuit operating to close or open the switching circuit according to the detection of the voltage at an end of the capacitor. Thus, the switching circuit operates on and off to generate pulses with frequency depending on I.sub.2, hence, depending on V.sub.cc. Methods for controlling the frequency range of the oscillating circuit and the rise time to fall time ratio of the pulses by introducing additional constant current supplying sources are also disclosed.