[sdiy] best way to convert bipolar to Cmos compatible square/gate?

[Neil Johnson]

Hi,

Oscar Salas wrote:
> A common op-amp as comparator followed by a 30K resistor to the CMOS input
> does the job.

It can, but you have to know about and accept the limitations of this 
approach.

http://www.analog.com/static/imported-files/tutorials/MT-084.pdf

> CMOS input has clamping diodes to its rails. Maximum Rating is I think (
> see your data-sheet) 10mA. So for a +/-15V supply a 30K will limit the
> current through the clamping diodes about 5mA.

This may be OK for DIY, but unless the manufacturer of the logic device 
specifically supports this mode of operation I wouldn't advise it for a 
commercial product.  You need to be aware of SCR latchup for example.

Neil
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