IR photosensor sees lots, tells enough
By Bill Schweber -- EDN, October 16, 2003
With all the attention that RF-based cordless links are getting, it’s easy to forget that IR connectivity finds use in millions of units for those ubiquitous specific-function consumer-product remote controls, as well as general sensing applications, such as smoke detectors (Picture). Fairchild’s QSB34 IR PIN-diode photosensor has a large 3×3-mm surface area and 120° reception angle, along with a transparent daylight filter for 880- to 940-nm light.
Flux response is typically 0.4A/W at 900 nm for this device, which also has just 25 pF of capacitance and 20-nsec typical rise and fall times. Overall dynamic range is 60 dB. The 1.25-mm-high photosensor is available in a gull-wing package for topside mounting and another package for under-board mounting; you can also mount it on the rear of a pc board to allow easier installation of EMI shielding. It sells for 22 cents (1000).
Fairchild Semiconductor Corp, 1-207-775-8100, www.fairchildsemi.com.
