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LM324LV: Opamp output at VCC removed condition

Jebin Satheesh Kumar
Intellectual 290 points

Part Number: LM324LV

Hi,
   What would be the output voltage level when VCC removed from the LM324LV in Voltage follower mode.

Conditions:-
    Non-inverting pin input voltage - 0.8V and VCC 0V (OFF).

Jebin

  • 0
    TI__Guru**** 174396 points
    Jebin,

    If non-inverting is +0.8V then there is enough voltage to forward bias the diode from input to VCC. Therefore the input current will try to power up VCC (minus the diode voltage drop). Use a series resistor on the non-inverting input to limit current to less than 1mA and accept that VCC will rise. If VCC rises enough, the output will become active. This won't happen for +0.8V

    If non-inverting is -0.8V then there is enough voltage to forward bias the diode from input to ground. Therefore the input current will be collected by various nodes in the op amp. Use a series resistor on the non-inverting input to limit current to less than -1mA and accept that other pins including output might no negative slightly.

    These general rules apply to almost all modern op amps.
    Is your input +0.8 or -0.8V? Is there a series resistor? Would any of the side effects mentioned be an issue?
  • 0 in reply to Ron Michallick
    TI__Guru**** 174396 points
    Jebin,

    Is your question resolved or do you need more time to reply?
  • 0 in reply to Ron Michallick
    Intellectual 290 points
    Hi Ron,
    Thanks for your replay.