My latest project got me into CMOS and I realize that I don’t understand the difference with all the different logic levels. I’m reading about TTL vs CMOS and all the variations. It’s history for some of you. It’s new to me. I plan on having more fun with these chips in the future and would like to understand them better. Is it wrong to find this so interesting? Does anyone know a good article to read about them?

 

This might be interesting: https://web.archive.org/web/2015010...rchildsemi.com/application-notes/AN/AN-77.pdf

 

google : ttl and cmos logic levels
You can find much more and you can also pick one like this table --
Logic Threshold Voltage Levels.

 

hi W,
Look at this image and the link.
https://www.google.com/search?q=logic+level+comparision+tables&ie=utf-8&oe=utf-8&client=firefox-b

E

 

Scan this site for useful info

https://www.allaboutcircuits.com/textbook/digital/chpt-3/logic-signal-voltage-levels/

 

Hello,

The following pictures might give you some idee about the logic levels:





Bertus

 

Yakov - very good article so the difference is like the name transistor vs Mosfet - explains the building block very well... How about LSTTL... using shottky? - confusing that datasheet calls this CMOS but it's called LS"TTL"

Am I wrong to assume that 3.3V logic should work with 5V TTL without level conversion due to the wide gap in logic high?

eric - diagrams always help..
bertus - the series comparison diagram helps...
scott and papa - more great stuff to explain...

 

Am I wrong to assume that 3.3V logic should work with 5V TTL without level conversion due to the wide gap in logic high?

To see the practical values of IC then you can check the ViH, ViL, VoH, VoL for DM74LS00(FairChild), SN74LS00(TI).

 

Found a great article - it answers all my questions... wow very interesting stuff! I miss having a subscription to nuts and volts... takes me back. This whole series is amazing read.

https://www.nutsvolts.com/magazine/article/understanding_digital_logic_ics_part_4