IC families

Discussion in 'General Electronics Chat' started by Nathan Hale, Jul 3, 2015.

  1. Nathan Hale

    Thread Starter Active Member

    Oct 28, 2011
    125
    2
    Hello folks! hope all is well.
    I have a question regarding digital electronics.
    I have seen quite often that there exist ICs out there that do the same exact operation but have different part numbers.
    are there subtle differences in these ICs?

    For example take the 74H78 which is a 2 dual positive pulse triggered J-K flip-flop with preset, common clock, and common clear
    and the ............ 74L78 which is also a 2 dual positive pulse triggered J-K flip-flop with preset, common clock, and common clear

    or take the
    74795 octal buffer with three-state outputs
    74796 octal buffer with three-state outputs
    74797 octal buffer with three-state outputs
    74798 octal buffer with three-state outputs

    Why do they bother making different ICs if only one of them will do the job.

    thank you for your replies!
     
  2. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    1) yes
    2) because every family of chips is optimized for some particular characteristic, like high speed, less power, etc.
     
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  3. crutschow

    Expert

    Mar 14, 2008
    13,000
    3,229
    The H and L series (as will as the S, LS, C, HC, etc.) all have different electrical characteristics (speed, power, etc.) and thus are used in different design situations to perform the same logic functions.

    If the last 3 or 4 numbers of the device are different then they likely have some subtle differences in their operation or pinout, even though their simple functional description may be the same.
     
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  4. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,523
    1,247
    Also, some series are much older than others. Standard TTL begat S (Shottkey) and LS (Low-power Shottkey), both of which were later surpassed by ALS (Advanced Low Power Shottkey). About 4-5 years after TTL arrived, RCA developed commercial CMOS parts with identical functions, less speed, way less power, and completely different part numbers. After 50 years of continuous development there are remnents of many different generations floating around.

    As for the four parts 795-798, read the data sheets.

    ak
     
  5. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,386
    497
    I recently bought 8051 microcontrollers, one has E, the other has V. E works on 5 volts. V is the "low voltage" variant that works from 3.3 volts.
     
  6. DickCappels

    Moderator

    Aug 21, 2008
    2,650
    632
    What might be so obvious it is not stated is that the numbers are carried into the new families to keep things much simpler than they otherwise would be. For example when you see 74H78 you can be pretty sure it has the same functionality as the 74L78, and the difference being a function of the respective family as mentioned by #12.
     
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