Driving PMOS with Window Comparator

Discussion in 'General Electronics Chat' started by rahdirs, Jun 10, 2013.

  1. rahdirs

    Thread Starter New Member

    May 22, 2013
    Hi all,

    I designed an inverting type of window-comparator i.e. if the input is between the two limits,output is low.This is shown in schematic 1 & works fine.

    But when i use the fact that output is low when input is between the two limits to drive a PMOS,then some-how the voltage doesn't drop to zero even within the window.What am i missing here ???

    Don't be worried about battery over there,i'll use a charge-controller to limit current.
  2. crutschow


    Mar 14, 2008
    Your are missing the fact that the diodes block any reverse current so there is nothing to discharge the gate capacitance and pull the PMOS gate voltage low. Add a 10k resistor from the gate to ground.
    rahdirs likes this.