Constant current circuit and an oscillating circuit controlled by the same
US5146188A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 25, 1991 |
| Grant date | Sep 8, 1992 |
| Priority date | — |
| Expiry date | Sep 25, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K4/502
- WIPO fieldControl
- WIPO sectorInstruments
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…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.