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I was trying to make an op-amp, but it turned out to be no good. Instead, it has a high slew rate (switches fast), and works well with positive feedback, making it a fairly good comparator -- I think! Criticism welcome. :) I didn't test it as much as I wanted to, testing was mind-numbing.
Published with positive feedback. Switch the SPDT in the lower middle to see it simply compare voltages. The other two switches just mark the inputs.
SPST switch marks the inverting input, NC pushbutton marks the non-inverting input.
Despite the fast switching it's not very quick overall, having a high propagation delay. Don't use negative feedback, it'll oscillate because of the slow propagation and fast slew rate. It may have an offset problem.
The junk in the bottom right corner is for decoupling AC. It responds much faster than a normal C-R decoupling, making it better for simulation.
~ Comparator Stats
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offset voltage 35 +-1μV (now dubious)
gain: more than 1.8MV/V with 40V supply
slew rate: ???
delay: up to 6μs
Other good points:
* Almost rail to rail output
* Single rail operation, balanced supply not needed
~ Construction Notes
~~~~~~~~~~~~~~~~~~~~~~
2μV source: oh dear...
0V source: positive max. :)
offset voltage:
+in +35.5 +-0.5μV
-in -35 +-1μV
>> does this even apply now power is switched? i saw offset going to over 4mV in the op-amp. -- oops: i wired -v wrong from the relay.
finding slew rate with 2vpp square wave source. looks perfect at 1ms period, horrible at 10us. it's reasonable at 20us, apart from he propagation delay. it's a long delay, maybe near 5us, and then a sharp switch. that's +in. -in has a much longer positive-going delay, but shorter negative-going. (may have swapped inputs.)
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