[optoelectronics.perkinelmer]

Description
Phototransistors are photodiode-amplifier combinations integrated within a single silicon chip. These are combined to overcome the major fault of photodiodes: unity gain. Many applications demand a greater output signal from the photodetector than can be generated by a photodiode alone. While the signal from a photodiode can always be amplified through use of an external op-amp or other circuitry, this approach is often not as practical or as cost-effective as the use of phototransistors. The phototransistor can be viewed as a photodiode whose output photocurrent is fed into the base of a conventional small-signal transistor. While not required for operation of the device as a photodetector, a base connection is often provided, allowing the designer the option of using base current to bias the transistor. The typical gain of a phototransistor can range from 100 to over 1500.

FEATUREs
• Low-cost visible and near-IR photodetection
• Available with gains from 100 to over 1500
• Moderately fast response times
• Available in a wide range of packages including epoxy-coated, transfer-molded, cast, hermetic packages, chip form and surface mounting technology
• Usable with almost any visible or near-infrared light source such as IREDs, neon, fluorescent, incandescent bulbs, lasers, flame sources, sunlight, etc.
• Same general electrical characteristics as familiar signal transistors

Typical Applications
• Computer/business equipment
    • Write-protect control
    • Margin controls—printers
• Industrial
    • LED light source—light pens
    • Security systems
    • Safety shields
• Consumer
    • Coin counters
    • Lottery card readers
    • Position sensors—joysticks
    • Remote controllers—toys, appliances, audio/visual equipment
    • Games—laser tag
    • Camera shutter control