Phase advance for ambient light suppression in phototransistors
US5091640A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 24, 1991 |
| Grant date | Feb 25, 1992 |
| Priority date | — |
| Expiry date | Jun 24, 2011 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08C23/04
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
The invention provides an oscillatory suppression circuit (54) for use in a photosensor loop circuit (10) employing a phototransistor (14). The oscillation suppression circuit (54) prevents oscillation in the photosensor loop circuit (10) caused by detected unmodulated high frequency light. The oscillatory suppression circuit (54) includes a resistor (58) and a capacitor (62) connected in series, and also connected in parallel with a base resistor (38) of a feedback transistor (26). The oscillatory suppression circuit (54) adds a small amount of phase advance to a feedback circuit (50). This small phase advance counteracts any additional negative phase shift produced when intense light pluses are detected by the phototransistor (14) and amplified by the high gain of the feedback circuit (50).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.