how do u increase the sensitivity of an IR sensor? what are the options?
If you're talking about an NPN IR photo-transistor, use it in a darlington arrangement with another sensitive NPN transistor.
In other words, use it to make a collector-base connection on another NPN transistor. Then, if there's a potential across the second transistor's collector-emitter junction any IR on the phototransistor will "turn on" the NPN transistor.
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