re act in article qhrq innlri crcnis unl edu mpaul unl edu marxhausen paul writes ok what s a quick rundown on all the series variations we re repairing something with a act on it and the question arises well do i really need the act part flipping through digi key i see als as c hc ac acq act hct acht hctls here s something i posted about this a few years ago it s not fully up to date with all the new variations some of which are just different manufacturer s synonyms in practical terms ignoring the technological details this is my view of the families nb i am not a giant corporation which influences my views on things like availability and backward compatibility the original speed good power consumption fair effectively obsolete now use ls or later except for a very few oddball functions like which are hard to find in newer families h modification of for higher speed at the cost of higher power consumption very obsolete use f l modification of for lower power at the cost of lower speed very obsolete use cmos s later modification of for even higher speed at some cost in power consumption effectively obsolete use f ls combination of l and s for speed comparable to with lower power consumption best all round ttl now widest variety of devices f fast as blazes power not too bad the clear choice for high speed in ttl availability and prices generally good as failed competitor to f although a few as parts do things that are hard to find in f and thus are still useful als possible replacement for ls generally souped up still fairly new availability and prices possibly a problem c fairly old family cmos devices with ttl pinouts competed with series not too successfully obsolete use or newer cmos families thrown in as the major non non ecl logic family the old cmos family still viable because of very wide range of devices low power consumption and wide range of supply voltages not fast very forgiving and easy to work with beware static electricity but that comment applies to many other modern logic families too there are neat devices in this family that exist in no other the clear choice when speed is not important hc a new attempt at pinout cmos fast compared to old cmos power consumption often lower than ttl possibly a good choice for general purpose logic assuming availability and affordability cmos logic levels not ttl ones beware very limited range of supply voltages compared to older cmos also major rise of power consumption at faster speeds hct hc with ttl logic levels much the same comments as hc read the fine print on things like power consumption ttl compatibility in cmos involves some compromises k thrown in for speed freaks the low end of ecl various sources claim that it is easier to work with than super fast ttl for serious high speed work less forgiving though read and follow the rules or it won t work availability to hobbyists limited can be expensive k for real speed freaks hot ecl harder to handle than k and inconvenient packages much more useful datasheets however as for compatibility between families the families except c and hc are all more or less logic level compatible but how many x devices you can drive from one y output varies enormously with x and y you just have to read the specs and do the arithmetic c and hc are compatible with the others with a bit of hassle compatibility can be a bit of hassle or a lot of hassle depending on what supply voltage is using k or k to anything else is considerable hassle me i use and ls with a sprinkling of f hc t and k are interesting but i haven t used either significantly yet all work is one man s work henry spencer u of toronto zoology kipling henry zoo toronto edu utzoo henry
