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Do you need a phototransistor circuit for electro-optical systems?
Your next electro-optical system might need a photodiode circuit. When we think of optical sensors, we usually think of something like a CCD, CMOS sensor, or photodiode. However, one very useful option is a phototransistor circuit.
How does a phototransistor work as a switch?
In other words, a phototransistor acts like a switch with a built-in threshold. When incident light is intense enough, the base-emitter voltage becomes small enough that a current easily flows through the device. This switching behavior makes phototransistors useful in a number of applications that require an ON and OFF state.
What makes a photo-Darlington phototransistor too slow?
A photo-Darlington is basically a phototransistor internally coupled to a second transistor. The emitter of the phototransistor feeds the base of the second transistor to gain increased sensitivity. However, the gain in sensitivity results in a slower response, which can make the Darlington phototransistor too slow for switching logic circuits.
Which is an example of a phototransistor transistor?
A phototransistor is effectively a standard bipolar transistor with a transparent case that allows light to reach its base-collector junction. A phototransistor can have high photoconductive gains through transistor action.16 Take an N 1 PN 2 phototransistor as an example.
How to change model name of unijunction transistor?
The prefix must be X for a subcircuit, and the model name must be the same as given in the file itself, which is X2N6027: c. Make sure the pin numbers in the symbol (right click to see the info) are in the same order as in the file. Leftmost is pin 1, and so on, so right click and alter each pin number if necessary (and name if desired):
How are photodiodes and phototransistors similar to each other?
Just as photodiodes have similar structure as a regular diode, a phototransistor has similar structure as any other transistor. These are generally built as NPN or PNP bipolar transistors, or as FET transistors. The base/gate in these transistors is triggered by incoming light, which excites charge carriers in this region.
Do you need SPICE model for phototransistor circuit?
Some manufacturers produce SPICE models for phototransistors, or for circuits that include phototransistors. Because the incident photon flux cannot be observed directly, the base/gate current generated in a phototransistor needs to be simulated with a current source.