[Arm-netbook] help needed with a ttl logic circuit

Luke Kenneth Casson Leighton lkcl at lkcl.net
Tue Aug 25 13:28:27 BST 2015

this one.  perfect :)  and ends up at $0.15 in 1k volumes, which is tolerable.


table 4.5 electrical characteristics show a wide range of (suitable)
Hi-in and Low-in voltages, depending on the supply input current.

then, for the 3.3v output side... the critical one V-out-low iiis....
maximum of 0.2v yay!  even if 4.5v was used it would still be a 0.35v
output.  V-out-high is

i know it's not the same as a one or two $0.02 transistors/FETS.  i've
seen some tutorials online that explain the operation of "proper"
buffer circuits like this one, it's a mad number of components: 5 or 6
transistors, 3 diodes, 4 resistors, just to ensure fully-on and

ooo wait a minute!

 dominique, if you look at that section, it explains that the first
transistor is in "reverse-biasing" mode when the inputs are high.
later on that section says that when the 1st transistor goes through
its "active" region it very quickly draws current away from the base
of the output transistor.  means "fast switching".

 oooo i'm tempted to use that.... :)


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