and can anyone explain why there is a demodulator in the circuit?
Im looking at the tsop4838 ir receiver modules and I want to use them in a laser circuit however I can't find a laser that is both safe and capable of working with the sensor so I want to build one of the detectors out of discreet components and tailor it to work with a red or green laser pen.From the documentation it appears a photodiode is connected to an amplifier (which I assume is a transimpedance op amp circuit) then a band pass filter and then a demodulator. Would this just be a matter of a few simple op amp circuits or would it get more complex than that and can anyone explain why there is a demodulator in the circuit? I can't see which signal is being demodulated as i thought the circuit just passed through whether the signal was high or not and whatever microcontroller the tsop was attatched to did all the demodulating?
Ah I see! So even if you shone an infrared lamp at it it wouldn't pass the signal through because the frequency of ir pulses (it wouldn't even be a pulse, just constant on) would be outside the accepted range?
Yes, the receiver only amplifies the base frequency, and ignores the "static" sun light, and mains frequency modulated light. TSOP4838. The last two digits is the frequency. 38Khz.If you look at the waveform picture from Krupski, you see the thin lines representing the base frequency.The receiver removes them, and just outputs the big blocks. The actual data.Leo..