How do I identify if a component is a photo diode or photo transistor? I have a three lead component removed from an old mouse where it was used to do quadrature encoding of the scroll wheel (a normal side facing IR LED was illuminating other side of the wheel) - presumably it houses two photo detectors side by side to distinguish which direction the wheel was being turned. What tests can I do to determine if it is a photo-transistor or photo-diode and appropriate parameters to drive it? I would like to re-purpose this for a micro-controller project I'm working on.
Only markings on the package is "H6.26" on the back and 'EL' on the top.
Managed to trace the two outer pins directly to separate pins on an unidentifiable micro-controller - (each trace is well below 1 Ohm). As for the middle pin it connects through a 10 Ohm resistor to I don't know where