• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 49 subscribers
  • Views 597 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM324LV: Opamp output at VCC removed condition

Jebin Satheesh Kumar
Intellectual 280 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*** 140136 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*** 140136 points
    Jebin,

    Is your question resolved or do you need more time to reply?
  • 0 in reply to Ron Michallick
    Intellectual 280 points
    Hi Ron,
    Thanks for your replay.