The LM393 and LM339 are the companion comparators to the LM358 and LM324 single supply operational amplifiers. The LM392 is a 358 operational amplifier and 393 comparator in a dual operational amplifier package.
The 391 is suppose to be a single 393/339.
The comparator response time has nothing to do with output rise and fall time. (1) A slow comparator like the 393/339 will have no problems driving fast logic.
High speed comparators are expensive because for high performance they need different processes (e.g. fast PNPs). A somewhat tricky combination is high speed and a large possible input differential.
The old 10 nanosecond NE529 and 5 nanosecond AM685 comparators are all NPN. These were alternate sourced and might have been considered jellybean parts (for high speed comparators) before the LT1016 came out. Any ECL differential line receiver is an all NPN fast comparator.
The LT1016 was a major improvement over older high speed comparators because it was stable in its linear range making it much easier to apply. That strobe pin is not just there for logic strobing; it also allows the comparison to be made at a time when the comparator inputs are not crossing their linear range to prevent the comparator from oscillating.
As I recall, there wasn't much in the space between ancient LM393alikes (~ 200ns, 300uA) and the screaming-fast ones (<8ns), with the MCP and TS3021 being some of the few examples (~ 50ns, 100uA). Hmm, I forget offhand what the fast ones typically draw for Icc.
I think just about everybody who second sourced the 311 back in the day had some 40 to 60 nanosecond comparators of their own, but they were never as popular as the slower and faster parts. The comparator function was just too esoteric. Faster ones like the NE529 and AM685 were more likely to be alternate sourced because they were so much more useful.
(1) Note that comparators have output *and* input slew rate limits. The output slew rate produces the rise and fall time but the input slew rate limit can cause problems with high speed input signals. See page 10 of the
LT1011 datasheet which is an improved 311.
Home
Help
Search
Login
Register
