Phototransistor apparatus with current injection ambient compensation
US4799044A · kind A · utility
33Cited by
6References
6Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Aug 6, 1987 |
| Grant date | Jan 17, 1989 |
| Priority date | — |
| Expiry date | Aug 6, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K17/941
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A current injection compensation circuit for dynamically compensating for the effect of ambient conditions on phototransistor output is disclosed. An output voltage is maintained at a nominal reference voltage level independent of ambient light input to allow use of a large output for a detected signal. Phototransistor current is a function only of ambient conditions, especially incident ambient light and is unaffected by compensation current injection. The ambient compensation current injection network can be employed with interactive touch input devices, such as infrared touch entry systems used with video displays.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.