I have a couple of fun electronics projects I have designed, very simple, that require some logic (i.e. cascading 555 timers and doing different things with logical combinations of their outputs).

I would need to use some AND/OR/NAND/NOR gates as well as some inverters, but it's not obvious to me what people normally use to prototype these. I've seen where to buy ICs containing gates, but looks there's not a lot of single gates available, they normally come in ICs with a few of the same type, and many times I just need one or two, and would prefer to not "waste" an IC containing 8. Also there are some options for through-hole, but not that many. For example, I inverters seem hard to find to mount through-hole. I have also seen IC with multifunction gates or mixed types of gates. I wonder if this is what's useful to have a bunch of spares of.

As an extra question, many times the same simple logic that I refer above can be recreated with a mux/demux. In cases like this, is there a preferred way to do it (logic gates VS mux/demux)?

  • Note: I know how to create logic gates from transistors, but that's not what I'm after.
  • \$\begingroup\$ "but looks there's not a lot of single gates available" There's every gate available in singles, and even a few compound gates. Look up "Little Logic". \$\endgroup\$ – Ignacio Vazquez-Abrams Jan 3 '17 at 1:18
  • \$\begingroup\$ @IgnacioVazquez-Abrams, but not if you want DIP packages. OP, don't worry about wasting gates. A 14-DIP IC with 8 NOT's or 6 AND's probably only costs $0.50 or $1. \$\endgroup\$ – The Photon Jan 3 '17 at 1:24
  • \$\begingroup\$ @photon: a 14 pin DIP will have 6 Nots/inverters or four 2-input gates (you need two pins for power and ground) \$\endgroup\$ – Peter Bennett Jan 3 '17 at 1:33
  • \$\begingroup\$ You should be able to find all the 74xx series logic you want in through-hole, e.g. 7404 inverter. Nobody has worried about wasting gates since the 1970s. But if you use CMOS, make sure you tie off the inputs of unused gates because you can have problems if they float. You might want to consider using an Arduino or microcontroller rather than logic gates, but that depends on what's fun for you. \$\endgroup\$ – Ken Shirriff Jan 3 '17 at 1:40

The "preferred" way to do it is the cheapest. Whether that leaves unused gates in a package or not is immaterial. Would you rather spend $2 for a single complex chip that would solve your problem, or $0.50 buying two simpler chips that also solves the problem, but leaves several spare gates.

  • \$\begingroup\$ Hi Lawrence. Since these are for fun and home-hacking, and not to produce many units, the cost is not always relevant for differences of half a $ or a couple of $. For example real state in the board or the enclosure are more important in some of the projects. \$\endgroup\$ – palako Jan 3 '17 at 1:24
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    \$\begingroup\$ @palako, then choose whatever reduces some other type of "cost"--- like the time it takes to get them from a vendor, or the amount of space they take up on a breadboard. \$\endgroup\$ – The Photon Jan 3 '17 at 1:25
  • \$\begingroup\$ Then look into using something like a 16V8 ( ATF16V8 are on the order of €1.20 a piece and you can fit a ton of logic into one ) \$\endgroup\$ – Lawrence NK1G Jan 3 '17 at 1:25
  • \$\begingroup\$ @LawrenceNK1G SPLDs are on the way out. As far as I know, Atmel is the only remaining manufacturer (Lattice and Altera got out of the business years ago), and the software is all ancient. \$\endgroup\$ – duskwuff Jan 3 '17 at 1:41
  • \$\begingroup\$ @duskwuff: Next you'll be telling me I can't get new 6SN7 in the steel envelopes. Well, at least I can still buy RCA MECL chips, right? RIGHT?? Oh G-d I feel so old. :D \$\endgroup\$ – Lawrence NK1G Jan 3 '17 at 1:53

There are chips with a single gate (TI calls them "Little Logic" and inserts "1G" into the name). However, they are are not available in through-hole packages, so you would have to put them on SMD adapter boards.

You get most flexibility with configurable logic gates, i.e., something like 74LVC1G97/98/99. (The older 74xx57/58 are not quite as flexible.)

Nowadays, logic isn't really used much; if there are multiple logic gates, it is often simpler to move everything into a microcontroller.


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