comparator reference voltage

Discussion in 'General Electronics Chat' started by eyuge2, Aug 13, 2009.

  1. eyuge2

    Thread Starter New Member

    Nov 18, 2005
    i have a question about the comparator LM311.
    we have a comparator circuit.a sigle voltag(+15V)supply the comparator, the referece voltage is connecting to inverting input,the value is 0.175V.
    at the TI LM311 datasheet,the common mode voltage min value is 13V to -14.5V. i think if the lower power supply value is 0V, the common mode voltage can't less than 0.5V.

    this circuit,the reference voltage is 0.175V,less than 0.5V. is the circuit is right?
  2. StayatHomeElectronics

    Distinguished Member

    Sep 25, 2008
    You are correct. The recommended operating conditions for V(in) is between Vcc(-) + 0.5V and Vcc(+) - 1.5V. Therefore, the recommended input range is between 0.5V and 13.5V for a single +15V supply. And, based on the V(common mode) the range may only reach 13V at the upper end.

    With a reference voltage of 0.175V, the circuit will probably not operate as you would like.
  3. Ron H

    AAC Fanatic!

    Apr 14, 2005
    Can you use LM393? Its common mode range includes zero volts.
  4. eyuge2

    Thread Starter New Member

    Nov 18, 2005
    thanks you!