please help me rregarding ic number

[gollapudi]

i m giving 5v suppy to 7408 AND gate and getting pulse o/p and giving its o/p to opto coupler but my optocoupler giving only supply voltage as output so what to do plz respond me.

 

[betwixt]

The output of the optocoupler is isolated from it's input so you can provide any different voltage for it. The maximum is decided by the manufacturers design, you will have to use the data sheet to find it out.

Brian.

 

[jiripolivka]

i m giving 5v suppy to 7408 AND gate and getting pulse o/p and giving its o/p to opto coupler but my optocoupler giving only supply voltage as output so what to do plz respond me.

An optocoupler consists of two devices: at the input there is a LED (which is fed with your 7408 TTL output, I hope through a resistor ~ 500 Ohms), at the output there is a phototransistor driven by the LED light output. The phototransistor (a switch) must be connected to the supply voltage and ground through a resistor (again ~500 Ohms), so its current interrupted by the input signal (LED light) will generate an on/off voltage across it.

Find a data sheet on your optocoupler, usually a basic schematic is included.