• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 208 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

OPA454: transient capability

Aaron Spaete
Expert 4527 points
Part Number: OPA454

Team, 

My customer has the following question. 

"i have selected OPA454AIDDAR IC for my design..i am planning to use it in voltage follower configuration with supply voltage of +11/-11V supply..output of this follower is connected to pin that will see transient of 20V for short duration..
My question is whether opamp is capable of withstanding short duration +20V/-20V transient even though supply voltage is +11v/-11V on both output pin and negative input pin whether 20V transient is acceptable."

 Regards,

Aaron

  • 0
    TI__Guru* 93105 points

    Hi Aaron,

    We certainly haven't tested the OPA454IDDAR under that transient condition, but its a JFET input op amp with back-to-back input clamps. JFETS usually have higher breakdown voltages than most of their bipolar counterparts.

    One of the most effective ways to protect an op amp input from an EOS condition is to incorporate input current limiting. Adding a series input resistor at the OPA454 non-inverting input will limit how much current can flow in the input circuit during an input transient event. The higher the resistance, the lower the current limit will be. If the circuit can tolerate a 1 kilohm series input resistor, then the maximum current from a 20 V input transient will be [(20 V - VF(ESD diode) -11 V ) / 1 kilohm], or 8.3 mA maximum. The ESD diodes are rated at 10 mA continuous so a 8.3 mA transient will not be an issue. If the series input resistor can be increased the maximum transient current will decrease. The OPA454 is a high-voltage op amp and if the supply voltage surge bit during from the transient it won't have any problem handling it. There shouldn't be a need to add transient voltage suppressor diodes to the supply lines.

    Note that the input resistor does add some thermal noise to the circuit. Therefore, it is best to find a compromise between a maximum allowable transient input current level and acceptable noise contribution.

    Regards, Thomas

    Precision Amplifiers Applications Engineering