I want to play around with some phototransistors and am curious about the base lead. It seems like this lead is treated as taboo . Some sources say it's just there but you won't have to or don't need to use it. Other sources say that it is there so that you can bias the transistor but don't go any further.
What effect does applying a bias current have on the function of the phototransistor? How is the characteristic curve different from a normal transistor when it is exposed to different levels of light? Saturation, active region, cutoff ...
Another experiment that I wanted to try is to cut the top off of a power transistor to make a homemade "power" phototransistor or combine it with a LED to make a homemade "power" optocoupler.
Any help would be greatly appreciated. Thanks