I'm trying to make an IR beam break detector, TSOP1738 is pretty neat, but it has gain attenuation and it makes things complicated for me.
I decided to use a simple IR phototransistor, I amplified the output by two Darlington pairs but the range is too short! It only works if the IR LED is within a few centimeters shining straight through. But TSOP1738 works very fine from meters away. Is it normal? What is inside receivers like TSOP1738? Is it a simple IR phototransitor with special amplification circuit?