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LM124 Opamp Output Protection

toseed khan
Prodigy 60 points
Other Parts Discussed in Thread: LM124, STRIKE

Hi,

As per LM124 datasheet don’t have ESD Protection.

The queries which I have:

1. How much transient/spike output pin of LM124 can handle without having protection?

2. If I do strike some amount of continuous voltage (say for millisecond) on output pin of LM124 How much LM124 can handle?

3. As per LM124 Datasheet the supply voltage range is upto 32volts if i do apply 32volts on the output pin of the opamp. Does the LM124 opamp will fail ?

or it can handle upto 32volts?

 

Waiting for your reply!

Thanks a lot in advance!

 

Regards

Toseed...

  • 0
    TI__Guru**** 166236 points

     Hello Toseed,

    The LM124 output does allow shorts to ground with some limitations. Shorts to VCC can cause permanent damage. Page 5 of the data sheet has this information.

    What is the full orderable part number?
    With this we can provide more information.

    Regards,
    Ron M.

  • 0 in reply to Ron Michallick
    Prodigy 60 points

    Ron,

    Thanks for your reply!

    The orderable part number is LM124DR.

    We are using this opamp at output section.So, there is chances that output pin of the opamp can see some amount of trasient/spike for very small duration say in micro second.

    Waiting for your reply!

    Thank you.

     

    Toseed 

  • 0 in reply to toseed khan
    TI__Guru**** 166236 points

    Hello Toseed,

    I ran some tests in the lab. If VOUT is forced more than 2V higher than VCC, a very large current will flow.
    This current can damage the LM124. Protection will need to be added to limit the output voltage.

    Regards,
    Ron M.

     


  • 0 in reply to Ron Michallick
    Prodigy 60 points

    Hi Ron,

    Thanks for your reply!

    We have one query about LM124 Rail to Rail Performance.

    In LM124 datasheet, High level output voltage (VOH) is Vcc-1.5 at room temperature (25 deg C) with Load 2k & VCC=5Volts. It means that we will get 3.5volts in high rail output.

    What will be the High level output voltage (VOH) at full temperature (-55 to 125 deg C) Considering same load 2k & VCC=5Volts?

    We want to know the headroom over the range of temperature if we will apply VCC=5 volts? What will be the high rail output in same load condition?

    Please reply me.

    Thanks,

    Toseed….

  • 0 in reply to toseed khan
    TI__Guru**** 166236 points

    Toseed,

    VOH has a temperature coeffcient of 4.05mV/C.
    So VOH is typically 405mV higher at 125C (vs 25C) & VOH is 324mV lower at -55C.
    The majority of the temp-co is based on two diode drops , -2mV/C each.

    Regards,
    Ron Michallick

  • 0 in reply to Ron Michallick
    Prodigy 60 points

     Hi Ron,

    Thanks for your reply!

    Is this temperature coefficient 4.05mV/C at room temperature 25 deg C?

    Is it Input offset voltage temperature drift? Where can I find this parameter in LM124 datasheet?

    I can see only Input offset voltage temperature drift in LM124 datasheet which is 7 uVolt/deg C.

    In datasheet, High level output voltage ( VOH) at room temperature (25 deg C) is Vcc-1.5 with Load 2k and VCC=5Volts. It means that I will get 3.5volts high rail output in same load and Vcc Condition.

    As you stated above at 125 deg C the High level output voltage (VOH) will be Vcc-1.5-0.405(Volts).   Is it correct?

    And also at cold means -55 deg C the High level output voltage (VOH) will be Vcc-1.5-0.324 (Volts).  Is it correct?

    I appreciate your reply in advance

    Thank you.

     


    Regards,

     

  • 0 in reply to toseed khan
    TI__Guru**** 166236 points

    Toseed,

    That temperature coefficient applies to the high output voltage only.

    Your math is correct.

     

  • 0 in reply to Ron Michallick
    Prodigy 60 points

     

    Hi Ron,

    In my schematic, LM124DR supply voltage (VCC) is 12VDC but as per datasheet, supply voltage (VCC) IS rated upto 32VDC.

    So, Can LM 124DR opamp handle 34volts transient at the output pin.

    Please confirm and waiting for your reply!

     

    Regards,

    Toseed…

  • 0 in reply to toseed khan
    TI__Guru**** 166236 points

    Toseed.

    On Jan 24 I "I ran some tests in the lab. If VOUT is forced more than 2V higher than VCC, a very large current will flow.
    This current can damage the LM124. Protection will need to be added to limit the output voltage."

    The output pin can higher than 12V if VCC=12V.

    Regards,
    Ron Michallick