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LM293: confuse about Vcm for OPA or Comparator

Albert Chen76
Intellectual 270 points
Part Number: LM293


Here's the example as shown.

1. is 5V for comparator Vcc sutible application because of postage input range is 0~3V even first stage of OPA is 24V?

 2. If Comparator Vcc should be 24V. does rail to rail input for Comparator is necessary?

  • +1
    Guru 318790 points

    1. The LM293's inputs need a headroom of 2 V to the positive supply. So using a 5 V supply for input signals in the range between 0 V and 3 V is OK.

    2. The LM293 has an open-collector output, so the output voltage is determined by the pull-up resistor. It does not matter whether you use 24 V or 5 V for the comparator's supply. You do not need rail-to-rail inputs because the input signals never reach the positive rail.

  • 0 in reply to Clemens Ladisch
    TI__Genius 11701 points

    Thanks Clemens for your support as usual! I hope this was able to help you Albert. Let us know if you have any more questions.