• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 48 subscribers
  • Views 227 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.

TLV9002: closed-loop -3dB bandwidth

Wesley Huang
Expert 1030 points
Part Number: TLV9002

Dear team,

For a typical low-side current sampling application as shown in the figure, CF and RF are usually used to set up a low-pass filter to filter out unnecessary low-frequency noise, and at the same time set a -3dB closed-loop bandwidth.

But in fact, since the GBW of OPA is not infinite, it is usually suggested that the GBW/(1+RF/RG) of OPA is several times more than 1/2pi*CF*RF. Is there any material that analyzes the theoretical basis and mathematical calculation process? I want to manually calculate what the corresponding closed-loop -3dB bandwidth will be under this circuit, assuming that I choose GBW not large enough.

For example: For the circuit in the picture, assuming that the input and output of the OPA are within the range of the specification, and the GBW selected for the op amp at this time is 1MHz (similar to TLV9002), what will the closed-loop -3dB bandwidth of the following circuit? Can you give me the calculation process, not just the empirical values and simulation results?

Best regards

Wesley

  • 0
    TI__Mastermind 24920 points

    Hi Wesley,

    I can't see the second image that you uploaded. I do see the first one's schematic though. 

    So we do have some some pieces of content that go in-depth to calculating filters. The first one,  Active Low-Pass Filter Design goes really in-depth on the very common low-pass filter designs we see customers use all the time. They don't match the circuit you are working with but they do show the mathematical calculations that you might be looking for. 

    We also have the Low-Pass, Filtered, Inverting Amplifier Circuit application cookbook circuit that goes into detail with the calculations as well and is much more similar to the circuit you are working with. The good thing about this document is it not only goes into GBW, but also helps verify that you chose a slew rate large enough to handle large signals if applicable to your system. 

    Let me know if this is what you were looking for. 

    Best Regards,

    Robert Clifton