Product number system: Plastic Emitters and Photosensors

Product numbers for Fairchild plastic emitters and photosensors consist of three letters followed by three numbers such as QEC123. Each digit has meaning and this application note will explain the method.

Product Number: Q E C 1 2 3

Digit: 1 2 3 4 5 6

Method
Digit One: This is always the letter 'Q' which stands historically for QT Optoelectronics.
Digit Two: This digit can be either the letter 'E' or the letter 'S' and signifies the function of the product. The 'E' stands for emitter and the 'S' stands for sensor.
Digit Three: This digit can be a 'B', 'C', 'D', or 'E' and signifies the package type. The 'B' stands for a subminiature or surface mount package. 'C' stands for a T-1 package. 'D' stands for a T-1 ¾ package. 'E' stands for a sidelooker package.
Digit Four: This digit codes the optical configuration (lens type, viewing angle).
Digit Five: This digit represents the chip type of the product. For emitters, a '1' indicates a GaAs chip, a '2' indicates a AlGaAs chip, and a '3' indicates a GaAs chip with an AlGaAs window. For photosensors, a '1' represents a small active area phototransistor, a '2' signifies a large active area photosensor, a '3' is for a photodarlington, a '4' a phototransistor with Rbe and a '5' an Optologic photodetector.
Digit Six: This digit indicates the selection of the product. A '1' is for the lowest bin which is the lowest radiant intensity or sensitivity. A '2' is the middle bin and a '3' is the highest bin.

Notes
1. The nomenclature for the product packages are characterized by the code 'T-#'. The number following the 'T' is the diameter of the lens in multiples of 1/8 inches.
2. The IR components above are sometimes referred to as 'discretes'.
3. To determine which emitters and photosensors make up the matched pair, please refer to the matched pair section of the short form catalog.
4. There are other plastic emitters and photosensors offered by Fairchild which do not follow this system. These products are legacy products from acquired companies such as Harris Semiconductor or are industry standards.
5. Some products use the 3 letters prefix (for instance QED) in conjunction with 3 or 4 digits that are identical to those used by competitors. Example: QSD2030 is a second source for Osram SFH2030.
6. Photosensors come usually in black color epoxy acting as a daylight filter. If the daylight filter is not required a suffix 'C' has to be added to the partnumber. Example: QSC113C.

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Sidelooker product color codes

Each IR emitter and photosensor in a sidelooker package is coded with a colored stripe on top of the package. The color codes for each product are given below. The codes are listed under two columns, past and current. The color codes for some products were changed on date code 9848. The color codes for the F5F1 and QEE123 were changed on date code 9901.

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Frequently Asked Questions (FAQs)

This product note lists and answers common technical questions about the operation of Fairchild's IR components.

1. What is the greatest distance at which an infrared solution will still work?
There is no absolute answer to this question. It depends much on the application. In most cases, by pulsing the emitter with a high drive current and using a sensitive photosensor, such as a photodarlington, one can expand the range.

• The range for detecting an object by reflection can be from 0 mm to 400 mm. The factors involved are the configuration and reflectivity of the reflective surface, the drive current of the emitter, and the photosensor output. Dust, however, can impair this range.
• Object sensing by transmissivity (i.e. breaking a beam of light between two points with an object) has a range of 0 to 12 m. The factors involved are the size of the object used to break the beam, the drive current of the emitter, the output type of the photosensor, and the electrical timing techniques used such as synchronous detection.
• For pure data transmission, the range is from 0 to 15 m. The factors are the data rate, the coding and modulation technique, and the expected signal to noise ratio or bit error rate. A high emitter drive current can improve the range of the system.

2. Can IR photosensors detect visible light?
Yes. All of the Fairchild photosensors are constructed using silicon chips. Silicon has a relatively flat sensitivity range and can detect the entire visible spectrum. The sensitivity, however, decreases from red wavelengths (660nm) to blue wavelengths (450nm). Most Fairchild photosensors, however, are sold with a daylight filter on the lens which blocks most visible light from reaching the sensing area of the chip. Depending on the needs of the customer, we can sell photosensors without the daylight filter. Curves are available showing the output response of the photosensor with and without a daylight filter.

3. Can ambient light cause Fairchild photosensors to false trigger?
The photosensors, as discussed in question two, are typically built with a daylight filter that prevents most visible light in the environment from reaching the detector chip. Curves are available showing the output response with and without a daylight filter. The response to light sources like fluorescent tubes, phosphorescent sources, or other artificial light sources depends on their spectral characteristics and may be noticeable.

4. What is the most efficient Fairchild emitter?
The brightest emitter we offer, in terms of on-axis intensity, is the QED123. This emitter has a narrow emission angle. If a wider emission angle is preferred, the QED223 or QED234 are recommended.

5. Can ambient light cause Fairchild photosensors to false trigger?
Each component type has a different response time which we specify as rise time or fall time. The typical rise times for each product family are given below.

• 940nm emitters: 1µs
• 880nm emitters: 0.8µs
• Phototransistors: 10µs
• Photodarlingtons: 100µs
• Photodiodes: 10ns - 50ns
• Optologic® Photosensors: 100ns (0.1µs)

6. What is the maximum driving current of Fairchild emitters?
The answer to this question depends on the type of emitter and the forward current conditions. Driving conditions can be either continuous or pulsed. The continuous maximum current is specified in the data sheet of the product. The maximum pulsed current depends on the pulse width and the duty cycle. The duty cycle is determined by dividing the pulse width by the period of the pulse. The pulsed current can range as high as two amps if the pulses are very short and the duty cycle is very low.

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