Electronics > Beginners
Operational Amplifier driving MOSFET
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Ian.M:
Twisted pair helps to prevent it picking up EMI, which, rectified in the B-E junction of the OPAMP input, could cause incorrect operation.   With a 1m cable run, I'd add the 2x 10nF caps as discussed to further shunt RF EMI away from the OPAMP input.
mike_mike:
I made a schematic with those capacitors.
Please have a look and tell me if the schematic is ok.
Ian.M:
Looks O.K.   Time to breadboad it, (with the MOSFET, its gate resistor, the diode and the MOSFET's supply and load connections soldered up on protoboard so no connections to/on the breadboard have to carry over 1/2A) and confirm it does what you want, then either lay out a PCB or develop a nice tight protoboard layout.
mike_mike:
Thanks for the reply.
You said in one of the previous post that LM393 (comparator)
 is better for this design.
It will be fine if i will use LM358 or I shoud switch for LM393 ?
Ian.M:
Not me.   You could switch to a comparator, but a LM393 isn't the best choice.  Its a dual comparator with open collector outputs, and for driving a single MOSFET gate, you'd be better off with a single comparator with a push-pull output stage.   However for such a slow circuit, (limited by the ORP12 and the load) there's no reason not to stick with an OPAMP.
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