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I want to make an ideal diode using a comparator and one p-channel mosfet. I'm looking for a cheapest method to add a few millivolts (25mV - 50mV) as an offset to one of op-amp's inputs just to ensure that the mosfet would be forward biased.

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    \$\begingroup\$ a couple of resistors? \$\endgroup\$ – Neil_UK Aug 30 '17 at 16:32
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    \$\begingroup\$ You have many choices on input bias current voltage drop, balancing Req input offset V, input offset current, thermal drift etc so make wise choices in each R selection and Comparator to meet your target offset. Which spec do you not understand? \$\endgroup\$ – Sunnyskyguy EE75 Aug 30 '17 at 16:36
  • \$\begingroup\$ Yes, but wouldn't be there any problem due to tolerance? I believe that isn't precise method. I'd like something that can be in pass production \$\endgroup\$ – MrBit Aug 30 '17 at 16:36
  • \$\begingroup\$ Try looking up a precision rectifier or, are you after a power diode with zero volt drop? \$\endgroup\$ – Andy aka Aug 30 '17 at 18:16
  • \$\begingroup\$ I'd like to saturate a p-channel mosfet when its Vsd voltage is positive. Ideal diode make this but using a discrete mosfet and an op amp you could make it cheaper. I want to use it in battery backup system. My two voltages are close similar. But I do worry about resistor's tolerance. I will update a schematic as soon as possible. \$\endgroup\$ – MrBit Aug 31 '17 at 6:48

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