19 Sep
2013
19 Sep
'13
11:16 a.m.
Some have mentioned substituting 7438 as a lower spec
version. I see
from the datasheet that it does have the same schematic as the 7439.
However, it doesn't actually guarantee more than 16mA output sink current.
According to the 'TTL Databook for Design Engineers', 2nd Edition (Texas
Instrumnts), the 7438 (not LS or S or ...) is speciified to sink 48mA
-tony