5 Replies Latest reply on May 25, 2018 11:44 PM by ntewinkel

    CMOS (4000B) compared to TTL Low power Shottcky (74LS)??

    millertron

      Hello all,
      I am studying electronics at college and have been asked to compare the TTL Low Power Schottky (74LS) and CMOS (4000B) logic families.
      I have searched the internet for figures to compare but it seems that everywhere I look gives different values for the specifications that I require. Would any of you be able to give me general values for the:

      -Logic high and Logic Low Input current and ‘Fan In’

      -Logic high and Logic Low Output current and ‘Fan Out’

      -Propagation Delay

      -Noise Margin

      -Logic high and Logic Low input voltage levels

      -Logic high and Logic Low output voltage levels

      -Upper frequency limit

      for each of the TTL Low Power Schottky (74LS) and CMOS (4000B) logic families so that I can then compare them to each other to create my answer.

      I understand these values may be slightly different for different logic chips and manufacturers but I am just after a general overview. Component datasheets don't seem to give all the information that I require and they are all rather cryptic about some points as I guess these values are presumed by the fact they are members of these logic families.

       

      Any help would be amazing.

      Thanks

        • Re: CMOS (4000B) compared to TTL Low power Shottcky (74LS)??
          danielw

          In the days of old fashioned data books, each part had its own specific data but then there would be separate family data sheets that covered the input and output circuits. I would suggest go direct to the manufacturers website and have a look on there.  Rather than go straight to the data sheet, look at the technical documents where there will be application data and family information.

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          • Re: CMOS (4000B) compared to TTL Low power Shottcky (74LS)??
            jw0752

            Hi James,

            Paul Scherz, in his book Practical Electronics for Inventors Third Edition  ISBN 978-0-07-177133-7 has a nice section that compares the different logic families. If you can get your hands on a copy check out pages 755 through 763.

            John

            3 of 3 people found this helpful
            • Re: CMOS (4000B) compared to TTL Low power Shottcky (74LS)??
              fmilburn

              As well as the great advice above, I was taught if I saw a range to report the range as well as the source.  Just record and report the ranges in the literature.  

              3 of 3 people found this helpful
              • Re: CMOS (4000B) compared to TTL Low power Shottcky (74LS)??
                mcb1

                Check the datasheets from various suppliers.

                The good part nowdays is most are online, so you don't even need to buy the books.

                BUT some are not the complete datasheet, and depending on the manufacturer, may vary in how they present the information

                 

                Component datasheets don't seem to give all the information that I require

                I'd suggest you're not looking at the right datasheets.

                Keep looking and look for the information, not the title ie propgation is going to be a time measurement.

                 

                 

                The questions you're asking, are something you need to understand and be able to use, hence why it has been asked to do it.

                 

                 

                Mark

                 

                Edit ... damn keyboard keeps mixing up letters.

                3 of 3 people found this helpful
                • Re: CMOS (4000B) compared to TTL Low power Shottcky (74LS)??
                  ntewinkel

                  It sounds like the lesson is more about reading data sheets and less about the actual logic family details.

                  From personal experience I can say it's worth the learning curve

                   

                  To find them, I would start by picking a specific 74LS chip, and using google to find it. For example, take 74LS04, google for "74LS04 datasheet", and you'll find Texas Instruments has one in pdf form right near the top of the results list.

                  Page 5 shows a handful of what you're asking for.

                   

                  Then do the same for the 4000 series. Pick a specific chip, and search for the datasheet.

                   

                  I think Wikipedia will show you the list of possible chips for both types, but you probably just need a few representative chips of either type, like the NAND, AND, OR, NOT.

                   

                  Hope that helps!

                   

                  Cheers,

                  -Nico

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