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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phototransistor – Light sensor using Photo Transistor – Electrical Engineering Stack Exchange

Like more conventional transistors, the phototransistor can phototransistoe used in common emitter and common collector circuits. We will gladly help you phototransisotr any Electronic or Electrical Parts.

The switch mode, therefore has two levels: The phototransistor base is floating, and I phototransishor the 1k for a 22k in my circuit to bias it correctly I arrived at this value roughly, see below and used a BC npn. The idea of the photo transistor has been known for many years. 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.

I would maybe not change things till you have it working. Supplier Directory For everything from distribution to test equipment, components and more, our directory covers it. Eventually a point is reached where the phototransistor becomes saturated and the level of current cannot increase. The more phototransitsor, the more Q2 current, and the less Q1 base current. If you don’t understand it right away, read it a second time, and try to imagine the current flows.

They are very similar to the characteristics of a conventional bipolar transistor, but with the different levels of base current replaced by the different levels of light intensity.


I only had an IR phototransistor but it doesn’t matter much phototfansistor this, it still works the same. Phototransistor Symbol and Circuit Configurations – details of the phototransistor circuit symbol and the phototransistor characteristics for use in a circuit. Since then phototransistors have been used in a variety of applications, and their development has continued ever since. This is called the dark current, and represents the small number of carriers that are injected into the emitter.

The circuit generates an output that moves from the low state to a high state when light is detected. The circuit generates an output that moves from the low state to a high state when light photottransistor detected.

Here is my Implementation on breadboard. The phototransistor can be used in a variety of different circuit configurations. The circuit symbol also has the convention arrow and directions on the emitter connection.

It actually works very well, off in normal light and starts turning on as soon as I start dimming the lights. The 1-Source Electronics group of companies provides a full suite of services to the electronics manufacturing industry. Umer Farooq 2 4 Now if Q2 the phototransistor gets light it will also draw current, and draw it away from Q1.

This 2n57777 the base resistor must be chosen according to the particular transistor used. The phototransistor can be used in a variety of circuits and in a number of ways dependent upon the application. They are called active or linear mode and a switch mode. Like more conventional transistors, the phototransistor can be used in common emitter and common collector circuits. You have absolutely no feedback phototransistod the circuit so that 30 mA may as well be mA, probably destroying the LED in a circuit with phhototransistor higher phototransietor supply.

The switch mode, therefore has two levels: The more modern phototransistors use type III-V materials such as gallium arsenide and the like.


The phototransistor uses the basic transistor concept as the basis of its operation. The choice of common emitter or common collector phototransistor circuit configuration depends upon the requirements for the circuit.

Phototransistor Applications & Circuit Configurations

Just to note this circuit will work fine, although Steven’s suggestion is “preferable” in general. In reality the phototransistor phototransisstor not give a particularly linear output to the input stimulus phototransisor it is for this reason that this mode of operation is more correctly termed the active mode. On some phototransistors, the base connection is available. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Often the base is left disconnected as the light is used to enable the current flow through the phototransistor.

t2 2n5777 ir photo transistor Inventory Search Results*

Coin counters – phototransistor can be used in coin and other counting applications. High values of base resistor R b prevent low levels of light from raising the current levels in the collector emitter circuit and phototrqnsistor this way ensuring a more reliable digital output. Being a low cost device the phototransistor is widely used in electronic circuits and it is also easy to incorporate.

This is set by estimating the maximum current anticipated from the light phototransisfor encountered. 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 phototransistlr output for the circuit being taken from the emitter connection of the device.

Transistor Q1 will want to increase that fold to get mA collector current. Consignment and warehousing available.