Thunderchild
New Member
so I have a lm339 and a TL082 and need a speed of like 100 KHz will any of these do ? I found the slew rates on the datasheets but am sure how to make this into frequenzy. if these won't do it what will ?
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Thunderchild said:so I have a lm339 and a TL082 and need a speed of like 100 KHz will any of these do ? I found the slew rates on the datasheets but am sure how to make this into frequenzy. if these won't do it what will ?
Thunderchild said:yes I am as you may have seen I finally managed to simulate a saw tooth generator and begin to wounder what is best simulation or real building when I tried to ad the comparator it gave an error. crappy software designer.
so yes now I need the comparator and scrap the flipping simulation, which do you recomend I would like to go up to 100-200 KHz if possible but at the moment want to start with a motor speed control.
Nigel Goodwin said:Doesn't matter much for motor speed control, speed isn't an issue - but needs to be MUCH, MUCH, MUCH lower in frequency than that!
Actually, the LM339 (and most other comparators) gets faster with more overdrive. See the graphs below, which are from the National datasheet.raybo said:you should have posted a diagram or schematic so we all can see your application. by the specs i don't see amy problem if it is running at 100kc. it has a 5mv offset and 5 mv drive and looks like if the input drive is 100mv it streches to 1.5usec that relates to 666kc max operation with 5mv overdrive it is more the 1 Mkc. then basicly it is drive input as a function of overdrive.now at these max speed don't expect to look like a square wave not unless you provide some hysterisis which will make square and reduce freq. of operation.If you want speed you should have choosena lm119,219,319. same packgage but only 2 per.conclusion need overdrive to make it square need less drive to make fast take your pick.