[MinnowBoard] 1.6V output on gpio pin
ktait at venturesystemdesign.com
Mon Feb 8 20:35:40 UTC 2016
Yes it is a buffer in a sense. It is indeed a switch, which is all you
need. Current is regulated by the series dropping resistor, so it just
turns the led on or off. A fet requires very little drive current at
this level, on the order of microamps to turn on, so it presents almost
no load to the port pin.
A port pin has what's called a totem pole drive, either switched to 0 or
1, so this is a good mate to an fet.
A 'buffer' is just a logic amplifier. it's input requires a fixed amount
based on the technology, TTL,LS,HC,Ac..etc. each technology has a
different drive level and current requirement on the inputs, but the
Look up a data sheet for say a 74hc367 buffer and look at the specs and
you will see what I mean.
An 74HC07 is also a switch with open collector outputs, so this will
drive more than the input.
The ULN2805 series has more drive and these are commonly used to drive
relays with more current needs.
If you are interested in learning more about how all this works, then a
good starting point is the basics. Long ago Don Lancaster published a
book, TTL Cookbook that was what every engineer started with. Not sure
it is still in print, but I'll bet the library has a copy. It's easy to
Most of the principals discussed here still apply today.
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