Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Question about an op amp

  1. Mar 21, 2008 #1
    For the INA101, in the configuration for the most basic circuit with the TO-100 package, two 1 mircofarad capacitors seem to be required to be placed in parallel with the supply voltages. Why is this, and is it actually necessary for an operating circuit, since the circuit example with the Dip package has no such requirement? You can see what I am talking about on pg. 6 in the linked pdf.
    http://www.chem.duke.edu/~boris/datasheets/INA101.pdf" [Broken]

    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Mar 21, 2008 #2

    George Jones

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    They provide paths to ground for (possible) crap riding on the power supply voltages.

    Look at the second sentence under APPLICATION INFORMATION.
    Last edited by a moderator: May 3, 2017
  4. Mar 21, 2008 #3
    Sorry about that.

    Thanks for the quick reply.
  5. Mar 21, 2008 #4


    User Avatar

    Staff: Mentor

    And in general, decoupling power supply input pins is good practice, both for analog and digital devices.
  6. Mar 22, 2008 #5
    The bypass capacitors also help to keep the demons of oscillation at bay...
  7. Mar 29, 2008 #6
    Hey another quick question, for the power supply voltage, how close to +/-15 volts do I need to be to have the instrument work right? Is it correct that the op amp will work w/ a +/-5 volt to a +/-20 volt supply?

  8. Mar 29, 2008 #7
    The datasheet states that the minimum supply voltage is +/-5V and the maximum supply voltage is +/- 20V.

    Therefore, you may assume that the device will operate within its stated parameters over that range of supply voltages.

    Interestingly (?) enough, the Absolute Max supply voltage is +/-20V too, which would appear to be sailing a bit close to the wind... I suppose it depends on how absolute that max is.
  9. Mar 31, 2008 #8


    User Avatar

    Staff: Mentor

    Keep in mind that not many opamps will let you take the inputs to the rails, and not many will be able to drive their outputs to the rails. Look in the datasheet for the specifications for how close the inputs and outputs can go to the rails, and keep that limitation in mind in your design.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Question about an op amp
  1. Question about Op-Amp (Replies: 7)

  2. Op Amp Question (Replies: 1)