opto couplers

[Dave Halliday]

>     As I said before I don't know much about electronics so I am not sure 
>     what an opto coupler is. I assume it is used to create isolation, 
>     through optical means, to protect sensitive equipment. Am I correct?
It is a phototransistor bonded into a light-tight case with an LED.

Very handy for doing voltage isolation, changing voltage levels (using 
small levels to switch bigger ones like a relay ), isolation ( 
seperating one part of a circuit completely from another )

These puppies are more for switching - they are not linear so using 
them for analog can get trickey,  There is a series made by GE which 
has a photo-FET and is linear to a couple percent over a few decade 
range.
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