7400 Series Logic Chips - Page 1
Forum section: electronics / beginners

author: Legion
author_rank: Frequent Contributor
timestamp: February 25, 2014, 07:20:19 pm
content: I'm ordering some 7400 series ICs off of digikey. I'm going to be using them on breadboards to learn digital logic. Since there are lots of variants (LS, HC, HCT, etc), I was wondering if there's a particular type that would be best suited for breadboarding/learning?

author: SeanB
author_rank: Super Contributor
timestamp: February 25, 2014, 07:29:06 pm
content: For breadboarding use the HC or HCT, as they are mostly compatible with all the others in logic level, though not necessarily in fan out. They all will drive at least 5 LS inputs. The HC also have the added bonus of them being true CMOS devices and many ( though not all and YMMV depending on manufacturer) will work from 3V to 15V as a power rail. As regular and LS are getting thin on the ground you will find it hard to get them in any case in bulk unless they are old stock. Stay away from S and ALS unless you really need the speed, they are power hogs and in most cases will not work in a breadboard layout easily.

author: grumpydoc
author_rank: Super Contributor
timestamp: February 25, 2014, 07:30:32 pm
content: HC is probably the easiest to start with.The HCT (or ACT etc) versions exist to interface with the older TTL versions - the minimum TTL logic 1 output of 2.8V is not guaranteed high enough to drive the CMOS families inputs.You might find the following useful:http://en.wikipedia.org/wiki/7400_serieshttp://www.fairchildsemi.com/an/AN/AN-319.pdfhttps://www.fairchildsemi.com/an/AN/AN-368.pdf

author: uwezi
author_rank: Unknown
timestamp: February 25, 2014, 09:02:57 pm
content: I also would vote for the HC.In our student labs in a basic electronics course we actually freely mix vintage 74xx, 74Sxx (OOS, old-old-stock partly in cer-dip) with 74LSxx, 74HCxx, 74Fxx and 74ACTxx. There have beenno(!) problems which could be attributed to the mixing of different technologies. As long as you keep to breadboarding "simple" circuits (up to 4-bit full adders or LED dice) at moderate speed (some thousands of Hz) they should all be friends.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 25, 2014, 09:05:56 pm
content: Quote from: SeanB on February 25, 2014, 07:29:06 pm74Cis roughly equivalent to CD4000 series "metal gate", high voltage CMOS. I think... the outputs are weaker (~500 ohms Rds(on) vs. ~250 ohms for CD4000, at 10V or thereabouts)? Both 74C and CD4000 are useful from 5-15V (though a bit weak down at 5V), and still operable down at 3V (if rather weak and slow).74HC is the "newer" (since the '80s I think) "silicon gate", medium voltage, "high" speed CMOS. The maximum voltage is 7V, and should never be used much above 5V. The drive capacity is good (Rds(on) 50-100 ohms I think, at 5V). HC is useful from 2-6V, and still operable above, I think, 1.2 or 1.5V.For breadboarding, I would also recommend HC. LS is good too, but only if you can find everything you need.Do be mindful of static when working with CMOS. 74HC is more robust than very early CMOS was notorious for, or even CD4000/74C series, but it's not invulnerable. (Neither is 74LS, but it is harder to screw up.)CD4000 series is still very handy, especially interfacing with analog circuits, when you need just a little glue logic, or analog switches (e.g., CD4066) and stuff like that. For pure logic, it's kind of janky, with relatively slow speeds, and nonsensical pinouts; HC is better for that. (If you run across a CD4000 function that you wish you had in HC, check the 74HC4000 series of course!)QuoteAgreed. Also, AC, LVC, etc. All those fast ones will just go nuts on a breadboard, even oscillate at frequencies invisible to the average oscilloscope!Tim

author: Legion
author_rank: Frequent Contributor
timestamp: February 26, 2014, 04:25:05 am
content: Picked up a bunch of 74HCs. Thanks for the advice.