Photo diode or photo transistor?

Thread Starter

Hansen

Joined May 3, 2015
21
Use a photo transistor if the needed response is several microseconds or more. If much faster, a more complicated circuit using a photo diode would probably be the best choice.
If I use a photo transistor and remove the light, will it open the circuit, or is it latched?
 

DickCappels

Joined Aug 21, 2008
6,300
It will open. Very little current through the collector and emitter when it is in the dark.

Check out those links in earlier posts.
 

Thread Starter

Hansen

Joined May 3, 2015
21
If I don't want any current going through when it's dark, would a photo diode work? Note: I prefer not to add any resistors to the circuit.
 

crutschow

Joined Mar 14, 2008
24,709
If I don't want any current going through when it's dark, would a photo diode work? Note: I prefer not to add any resistors to the circuit.
Both carry no current in the dark, but the photo diode is much less sensitive to light (less current flows when illuminated).
What are you doing with the circuit if it has no resistors?
 
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