Comparator slows down LTspice

[ben7]

Hey, Im having trouble simulating a circuit with comparators in LTspice. Without the comparators, the circuit works fine, but with them the circuit immediately slows down. By slows down, I mean it goes about 10 microseconds per second!

Tried op-amps used as comparators, but with no luck.

I also tried almost all the comparator models ltspice comes with, and none of them worked any better. I also tried an LM339 model but it did the same thing!

Any ideas how to get the comparators to run better?

[b700029]

Re: Comparator slows down LTspice

It's a lot more complex simulating an active, non-linear IC like that than a simple resistor, transistor, or diode. I don't know about LTspice but there may be a precision option that you could decrease to trade precision for speed.

[ben7]

Re: Comparator slows down LTspice

It's a lot more complex simulating an active, non-linear IC like that than a simple resistor, transistor, or diode. I don't know about LTspice but there may be a precision option that you could decrease to trade precision for speed.

Yea there might be, I am new to ltspice too. And the circuit doesn't need to be very accurate either.

[PeteS in CA]

Re: Comparator slows down LTspice

Using an op-amp for a comparator should be slower - not optimized for coming out of saturation at the rails. An LM339 is a GP, low power, not super fast, comparator. Maybe look into seeing if NatSemi has a spice model available on their website for their LM319, which is very fast (but not low power). The LM319 is also one comparator per package rather than quad, like an LM339. The LM339 and LM319 are very old-school parts - designed in the early or mid 70s. There may be an inexpensive, more modern, very fast and low power parts available from NatSemi, TI, Linear Technology or Maxim.