Phototransistors

www.optoelectronics.perkinelmer.com

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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.

Phototransistors can be used as ambient-light detectors. When

used with a controllable light source, typically an IRED, they

are often employed as the detector element for optoisolators and

transmissive or reflective optical switches.

All phototransistors are RoHS compliant.

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

Principle of Operation

Phototransistors are solid-state light

detectors that possess internal gain.

They can be used to provide either

an analog or digital output signal.

Datasheets available upon request.

Absolute Maximum Ratings

Maximum Temperatures

Storage and Operating:

-40°C to 100°C

VTT1017, VTT1115, VTT1116, and VTT1117)

VTT7225, VTT7122, VTT7123, and VTT7125)

VTT9102, and VTT9103)

Continuous Power Dissipation: 50 mW

and VTT9103)

VTT1115, VTT1116, and VTT1117)

Derate above 30°C:

0.71 mW/˚C

and VTT9103)

VTT1115, VTT1116, and VTT1117)

Maximum Current:

25 mA

VTT1115, VTT1116, and VTT1117)

Lead-Soldering Temperature:

260°C (1.6 mm from case, 5 sec. max.)

phototransistors