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Essential Logic Families - Workbench Wednesdays 35

 

Did you know that TTL chips do not output 5 volts? 74LS, 74HC, and 74HCT all have different input and output thresholds. Switching between logic families can be difficult if you are not careful. In this video, learn how different 7400-series logic families compare with input threshold, output voltage, frequency, rise time, and propagation delay.

 

Supplemental Content:

Bill of Material:

Product Name Manufacturer Quantity Buy Now Buy KitBuy Kit
MC74HC1G04DTT1G - 1 Gate Inverter 74HC ON Semi 1 Buy Now Buy NowBuy Now
SN74HCT04NSN74HCT04N - Inverter 74HCT, DIP Texas Instruments 1 Buy Now Buy NowBuy Now
SN74LS04NSN74LS04N - Inverter 74LS, DIP Texas Instruments 1 Buy Now Buy NowBuy Now
SOT23-to-SIP Adapter Captial Advanced 1 Buy Now Buy NowBuy Now
LCQT-SOIC14LCQT-SOIC14 SOIC14 to DIP Adapter ARIES 1 Buy Now Buy NowBuy Now

 

  • Very Nicely Done.

    I started with TTL and a little ECL threw in. moved quickly to Tri-State even though they are now called three-state, I still prefer Tri-State. image Oh, yes don't forget about Fairchild 9600 family it falls somewhere between 74 and 74LS

    Typical Propagation Delays 74xx02 or equivalentCD4x7474LS74HCT74AHCT74FECL5vdc110 ns*262 ns13 ns5.5 ns5.5 ns260 ps260 ps

     

    ECL is STILL the fastest game in town But it is very power-hungry and you will need a welder to power them, image and they get very hot! cooling is a must!

    ECS is still being used in some avionics but normally the chips have a 1/4" plate on top of them.

     

    * at 15v prop time is 35ns

    ~~ Cris

  • in reply to baldengineer

    No it is not. Between synchronous and asynchronous logic, venders lying about their device capability, cross talk, noise, and trigger levels, it kept us quite busy to make a circuit work.

     

    That said, once you got familiar with the various chips, you could put a circuit together very quickly on a wire wrap board to test things out.

     

    Had a lot of fun and made a lot of very useful systems back in those days.

     

    DAB

  • in reply to DAB

    You had to spend a lot of time with the data books to make sure what was happening with some of the chips.

    Digital has never been as simple as everyone thought 1s and 0s should be, has it?

  • Good episode.

     

    I have spent many hours with TTL back when they were pretty much the only chips we had.

    They did the job, but you sometimes had to work around their limitations.

    You had to spend a lot of time with the data books to make sure what was happening with some of the chips.

     

    Thanks

    DAB