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Problem with output signal from THS3061

Majo Majo
Prodigy 40 points
Other Parts Discussed in Thread: THS3061, INA163

Hi everybody,

I decided to use for my biomedical application instrumentation amplifier INA163. Therefore that I don´t know how large the output impedance would be I would like to use unity gain buffer. So, I decided to use THS3061. The output from the THS3061 is going into the attenuator and subsequently into the AD8302 detector. The problem is that my signal from THS3061 has got a noise and the AD8302 is not able to detect this signal. I attached my connection. Please could you somebody help me. I don’t know what to do.

Thank you very much.

  • 0
    TI__Mastermind 25815 points
    Hello Majo,

    The output impedance of the INA163 is going to be extremely small in comparison to the input impedance of the THS3061, or any other amplifier's non-inverting node impedance for that matter.

    I suggest measuring the output of the INA163 using an oscilloscope to ensure that you are obtaining the expected output. If not, you will want to ensure that your power supplies are sufficient given your input's common-mode voltage and desired output swing. The common-mode range is given in the data sheet as 3V from each rail (typical). So, using +/-15V supplies your common-mode voltage is from -12V to +12V. A similar calculation can be conducted for the output swing.

    Assuming the INA163 is operating in a linear region and as expected, you can then start looking at the output of the THS3061. Personally I find it curious that a 300MHz CFA is in the signal chain after the INA163, which has ~1MHz BW when G=1V/V. Nonetheless, if you find that the issue is with the THS device and your do need a high-speed amplifier, I suggest posting the issue in our high-speed amplifier forum.