choosing buffer IC for driving optocoupler

[zizi110]

Hi all ,
i am trying to transmit a signal from a special module to micro controller, but based on datasheet of this module i should use an optocoupler between the module and micro, and also because of low output current of this pin of module it is necessary to use a buffer for increasing current for driving optocoupler:

one pin of module ==> buffer ==>optocoupler ==> micro controller

i don't know what kind of buffer IC there is for this case, please help ...

thanks

 

[FvM]

You forgot to mention most relevant details, e.g. kind of "module" and opto coupler, signal parameters.

In case of doubt, a simple transistor or a logic gate makes a perfect buffer.

 

[zizi110]

thanks FvM for your reply,
the module is FSBS15CH60 , i should connect VFO pin to micro .... but in datasheet noted that we should use optocoupler and buffer,
i have a SFH690 optocouler , about 20-25mA is sufficient for driving this optocoupler , but i dont know what kind of buffer ic can make such an current for opto ..... i mean the output current of VFO pin of module is about 1 mA, what buffer IC i can use for increasing this current to about 20mA?

thanks

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i found DM74LS240 and DM74LS244 ..... is it ok in this case?

 

[FvM]

VFO is open collector output with 5 mA rating, which should be sufficient to drive a sensitive opto coupler directly. Or use PNP transistor in common collector configuration.