phototransistor

Hello all I'm trying to make a small circuit in which i have to choose the resistance value.. can someone tell me how to choose the resistor value at the input of Optocoupler IC. And my input voltage is 3.3V .. and current 25mili amps ..

I have an IR sensor which is basically an IR emitter and a IR photo transistor. I have got a problem with it. I am powering it up via 5V. I have done slight modification, I have taken the emitter and photo-transistor apart and set them in a way that they are continuously facing each other. Now...

Hello, I have some questions regarding my implementation of IR LED detection with a phototransistor. Idea The main idea of the circuit is to make a circuit with incorporating a phototransistor, which will create a 0-5V signal on its output whether it detect IR LED presence. IR LED will be...

hello, I have to build an automatic gain control using an FET and an Operational Amplifier, for a phototransistor (SFH314) so that when the signal of an IR LED is weak the AGC maintains the signal, and when the signal is strong reduces it, the gate of the FET I have to control it with the...