Datasheet of 2N It is apparently a visible light phototransistor (also includes IR since no IR filter is indicated) –no wavelength is indicated. PHOTOTRANSISTOR. Part Number: WP3DP3BT. Features. ○ Mechanically and spectrally matched to the infrared emitting. LED lamp. ○ Blue transparent lens. The circuit you show should work as it is, since it is already for a phototransistor. Just leave your base lead floating. EDIT – the breadboard.

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The two phototransistor circuit configurations have slightly different operating characteristics and these may determine the circuit used. The switch mode, therefore has two levels: It was then only two years before the photo transistor was demonstrated.

What do I do? The common emitter phototransistor circuit configuration is possibly the most widely used, like its more conventional straight transistor circuit. This is set by estimating the maximum current anticipated from the light levels encountered. This is amplified by the current gain of the transistor in the normal way.

However as the level of light increases, current starts to flow.

As a result of their ease of use and their applications, phototransistors are used in lhototransistor applications. 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 phoototransistor device.


William Shockley first proposed the idea innot long after the ordinary transistor had been discovered. The circuit actually acts as an amplifier. I tried to make the two lines in parallel. Eventually a point is reached where the phototransistor becomes saturated and the level of current cannot increase. First move the LED to the transistor’s collector, and add a series resistor. Electrical Socket Relay Sockets Semiconductor: Often the base is left disconnected as the light is used to enable the current flow through the phototransistor.

The switch mode, therefore has two levels: Sometimes a Schottky metal semiconductor junction can be used for the collector within a phototransistor, although this practice is less common these days because other structures offer better levels of performance.

Phototransistor Applications & Circuit Configurations

Common emitter phototransistor circuit The common emitter phototransistor circuit configuration is possibly the most widely used, like its more conventional straight transistor circuit. I only had an IR phototransistor but it doesn’t matter much for this, it still works the same. All other aspects of ;hototransistor circuit function remain the same.

So if you are intending to eventually power this circuit from something else other than phototarnsistor coin cell, then you should go for the common emitter circuit Steven describes. Light sensor using Photo Transistor Ask Question.

What did you already try and how didn’t it work? If you don’t understand it right away, read it a phototraneistor time, and try to imagine the current flows. The circuit actually acts as an amplifier. This generation mainly occurs in the reverse biased base-collector junction. In fact a phototransistor can be made by exposing the semiconductor of an ordinary transistor to light. It can be seen that the phototransistor symbol shown does not give a base connection.


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This type of phototransistor mode is useful for detecting objects, sending data or reading encoders, etc. Both versions of the phototransistor symbol are phototfansistor and understood. I suspect my connectionof base of the transistor with resistor is wrong, correct me if I am wrong.

The phototransistor can be used in a variety of circuits and in a number of ways dependent upon the application.

t2 2n5777 ir photo transistor Inventory Search Results*

You now have a common collector phitotransistor, and the 2N’s base is at 2. Steven – In general yes, but we’ll have to agree to disagree on this one I think: Phototransistor characteristics As already mentioned the photo transistor has a high level of gain resulting from the transistor action.

The phototransistor symbol often has two arrows pointing towards it, but other phototransistor symbols show a jagged arrow. The base is at 0. The site you got the above circuit from also has an example of such a circuit:.