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About INA128 Application Question

Kuo Nowal
Expert 2315 points
Other Parts Discussed in Thread: INA128

Hi Sir,


May I know we can verification INA128 by as below circuit?

First stage is Buffer
Second stage is Inverting AMP
Input source is 1k Hz / 3V rectangular wave

  • 0
    TI__Mastermind 25795 points
    Hello Kuo,

    Here are some observations concerning your circuit:

    1) The positive power supply is grounded and connected to Vref. However, it looks like the input is +3V. In order to input a positive input signal you need a positive supply voltage. I suggest adding a +5V supply and grounding the reference pin.

    2) There is nothing connected to VIN+. Therefore the output of amplifier A2 will be undetermined and therefore operation will be undetermined. I recommend connecting VIN+ to a potential.

    3) Please ensure the amplifier is operating linearly. Please refer to the following FAQ:

    e2e.ti.com/.../3373.understanding-instrumentation-amplifier-vcm-vs-vout-plots

    I highly recommend downloading and installing the INA Common-mode Calculator. Here is a direct link:

    www.ti.com/.../ina-cmv-calc