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Old 08-31-2012, 02:17 AM
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citfta citfta is offline
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Join Date: Jun 2008
Posts: 1,309
Flywheel diode

Hi Ufo,

Yes I agree the flywheel diode is probably not needed on your motor however this drawing was shown as an example of how easy it is to use the proper chip for the job. You cannot get quick turn off times on the mosfet using the circuit you have posted. The gate capacitance is just too high to get quick turn off by trying to bleed off the gate charge with your resistor to ground from the gate. This simple chip takes care of that problem. That is what it was designed to do. If anyone can connect a 555 circuit and get it to work then they should be able to easily use this chip. Besides being easy to use it gives you great isolation between your timing circuit and your power circuit so you don't have to worry about any spikes getting back to your timing circuit and causing problems there.

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