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Phototransistors are photodiode-amplifier combinations integrated within a phototransistor can be viewed as a photodiode whose output. Phototransistor and IRED Part Number Index. Phototransistor Part . Phototransistors are solid state light detectors that possess internal gain. This makes them. The phototransistor has a light sensitive collector to base junction. A lens is used in a transistor package to expose base to an incident light. When no light is.

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What Is Phototransistor Pdf

We have seen in a previous experiment that the resistance of both a photodiode and a phototransistor changes as the intensity of the light hitting the device. PHOTOTRANSISTOR. Part Number: WP3DP3BT. Features. ○ Mechanically and spectrally matched to the infrared emitting. LED lamp. ○ Blue transparent lens. FUNDAMENTAL PHOTODIODE CIRCUITS. Figures 1 and 2 show the fundamental photodiode circuits. The circuit shown in Figure 1 transforms a photo -.

Phototransistor Includes: Phototransistors are ideal photodetectors and can be used in a host of different applications. Phototransistor circuits are normally relatively straightforward, especially of the detector is only required to detect the presence of absence of a particular light source. Phototransistor applications As a result of their ease of use and their applications, phototransistors are used in many applications. Opto-isolators - here the phototransistor is used as the light sensor, the light emitter being relatively close, but at a different potential. The physical gap between the light emitter and detector provides a considerable degree of electrical isolation. Position sensing - in this application the optoisolator can be used to detect the position of a moving element, often the moving element has a light or interrupts a beam of light which the phototransistor detects. Security systems - phototransistor can be used in many ways in security systems, often detecting whether a beam of light is present or has been broken by an intruder.

Like more conventional transistors, the phototransistor can be used in common emitter and common collector circuits. Common base circuits are not normally used because the base connection is often left floating internally and may not be available. If the base connection is required, then it is necessary to download a phototransistor with a base connection available.

The choice of common emitter or common collector phototransistor circuit configuration depends upon the requirements for the circuit. The two phototransistor circuit configurations have slightly different operating characteristics and these may determine the circuit used. Common emitter phototransistor circuit The common emitter phototransistor circuit configuration is possibly the most widely used, like its more conventional straight transistor circuit.

The collector is taken to the supply voltage via a collector load resistor, and the output is taken from the collector connection on the phototransistor.

The circuit generates an output that moves from a high voltage state to a low voltage state when light is detected. The circuit actually acts as an amplifier. The current generated by the light affects the base region. This is amplified by the current gain of the transistor in the normal way. Common emitter phototransistor circuit Common collector phototransistor circuit The common collector, or emitter follower phototransistor circuit configuration has effectively the same topology as the normal common emitter transistor circuit - the emitter is taken to ground via a load resistor, and the output for the circuit being taken from the emitter connection of the device.

Phototransistor Applications & Circuit Configurations

The circuit generates an output that moves from the low state to a high state when light is detected. The above equations shown that the collector current is directly proportional to the current base leakage current, i.

The phototransistor is made up of semiconductor material. The base of the phototransistor would only be used for biasing the transistor. In case of NPN transistor , the collector is made positive concerning emitter, and in PNP, the collector is kept negative. The light enters into the base region of phototransistor generates the electron-hole pairs.

The movement of electrons under the influence of electric field causes the current in the base region. The base current injected the electrons in the emitter region.

Phototransistor

The major drawback of the phototransistor is that they have low-frequency response. The construction of the phototransistor is quite similar to the ordinary transistor.

Earlier, the germanium and silicon are used for fabricating the phototransistor. The small hole is made on the surface of the collector-base junction for placing the lens.

Phototransistor Circuit Configurations | Applications | Electronics Notes

The lens focuses the light on the surface. Nowadays the transistor is made of a highly light effective material like gallium and arsenides.

The emitter-base junction is kept at forward biased, and the collector-base junction is at the reverse biased.

The base of the phototransistor would only be used for biasing the transistor. In case of NPN transistor , the collector is made positive concerning emitter, and in PNP, the collector is kept negative. The light enters into the base region of phototransistor generates the electron-hole pairs.

The movement of electrons under the influence of electric field causes the current in the base region.

The base current injected the electrons in the emitter region. The major drawback of the phototransistor is that they have low-frequency response.

The construction of the phototransistor is quite similar to the ordinary transistor. Earlier, the germanium and silicon are used for fabricating the phototransistor. The small hole is made on the surface of the collector-base junction for placing the lens. The lens focuses the light on the surface.

Nowadays the transistor is made of a highly light effective material like gallium and arsenides. The emitter-base junction is kept at forward biased, and the collector-base junction is at the reverse biased. When no light falls on the surface of the transistor, the small reverse saturation current induces on the transistor. The reverse saturation current induces because of the few minority charge carriers.