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THS3111: simulations do not translate to circuit.

nafis azad
Prodigy 30 points
Part Number: THS3111
Other Parts Discussed in Thread: THS3091, THS3095

I have included the Schematic of the simulation I was running. And its not translating to circuit. The IC is getting hot and the output is unstable.

Was wondering if I am not using the biasing resistors properly. This is my first time dealing with a Current feedback opAmp. So any feedback is appreciated.

Also, the Pin outs on the model is different from the DATASHEET. Am I missing something?

Thank you!

output.pdftest SCH.pdf

  • 0
    TI__Expert 6050 points

    Hi Nafis,

    I have reviewed your schematic and I do not see any immediate issues with your design. Can you please provide the following information:

    • When creating the circuit, can you confirm that you are using the pinout provided in the data sheet and not the numbers listed on the pins of the Pspice model
    • Can you provide more details describing how the output is unstable and not translating from simulation to circuit
    • Can you provide any pictures of your circuit or board layout 

    Thanks,

    Nick

  • 0 in reply to Nick Nauman
    Prodigy 30 points

    Hi Nick,

    i) The pinout used was from the datasheet.

    ii) As for the output, the circuit as in the schematic you see, heats up the IC. Its pretty hot to the touch, and the current draw from the supply is around 3W.

    I have also isolated U3 and tried to run it by itself with a grounded 50ohm resistor on the input. in this case, I do get a measurable output(I am testing with a 1kHz sine wave) But the IC starts drawing too much power and the output changes randomly.

    I am trying a different setup now, so do not have the circuit on the board.

  • +1 in reply to nafis azad
    TI__Expert 6050 points

    Hi Nafis,

    Please see this note from the Application Information section of the datasheet.

    I believe the behavior you are observing is a result of using a sine wave with the THS3111. Therefore I would recommend using a different device, such as the THS3091 or THS3095.

    Thanks,

    Nick