The phototransistor invention followed on from the development of the first point contact transistor. Initial development of the phototransistor
Understanding the various specifications is important for this. In view of the fact that these electronic components are cheap and easily available, it is necessary to ensure that the selected component meets the requirements of the circuit design in which it will be used. Phototransistors are widely available and can easily be obtained quite cheaply from electronic component distributors - in view of their use in many electronic circuits and applications, they are available as part of the standard semiconductor device inventory. Since their first introduction and use, phototransistors have been used in a variety of circuit designs and applications, and their development has continued ever since. It was then only two years before the photo-transistor was demonstrated. William Shockley first proposed the idea in 1951, not long after the ordinary bipolar transistor had been discovered. The idea of the phototransistor has been known for many years. Note the lens at the top and the fact that it only has two leads because the base is often left open circuit and no external connection is provided.
This makes phototransistors more suitable in a number of applications.Īlthough all bipolar transistors themselves are light sensitive, which is why most transistors are encapsulated in metal or plastic cans, phototransistors are a specialised form of bipolar transistor that have been optimised for its light sensitivity, making these electronic components ideal for many light sensing applications. Phototransistors and photodiodes can both be used for sensing light, but the phototransistor is more sensitive in view of the gain provided by the fact that it is a bipolar transistor. The phototransistor is a semiconductor device that is able to sense light levels and alter the current flowing between emitter and collector according to the level of light it receives. Phototransistor basics Applications & circuits Photodarlington Optocoupler / optoisolator What is a Phototransistor: tutorial & primer Phototransistors are a form of bipolar transistor that is sensitive to light - having the gain of a transistor they are much more sensitive than photodiodes and find uses in many light detection circuit designs.
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