Constant current-constant voltage circuit
US5047706A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 5, 1990 |
| Grant date | Sep 10, 1991 |
| Priority date | — |
| Expiry date | Sep 5, 2010 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S323/907
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
In a constant current-constant voltage circuit disclosed herein, gates of MOSFETs Q.sub.1 and Q.sub.2 are connected together, and the gate of the MOSFET Q.sub.1 is connected to the drain thereof. Further, the source of the MOSFET Q.sub.1 is connected to ground potential GND whereas the source of the MOSFET Q.sub.2 is connected to the drain of a MOSFET Q.sub.3 having a gate connected to power supply voltage V.sub.DD and a source connected to the ground voltage GND. A current mirror circuit including Q.sub.4 and Q.sub.5 has an input and an output respectively connected to the drain of the second MOSFET Q.sub.2 and the drain of the first MOSFET Q.sub.1. A first coefficient (W.sub.3 L.sub.2 /L.sub.3 W.sub.2) depending upon channel lengths (L.sub.2, L.sub.3) and channel widths (W.sub.2, W.sub.3) of the MOSFETs Q.sub.2 and Q.sub.3 is set at a value not larger than a predetermined value. Therefore, the MOSFET Q.sub.3 operates in a linear region as high resistance, and the MOSFETs Q.sub.1 and Q.sub.2 operate in a sub-threshold region. As a result, the dependence upon temperature is significantly improved.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.