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Hello,
I am trying to develop a low power EEG measurement system based on the INA333 ECG example showed in its datasheet. As I am planning to realize the design with the INA2141 I don't know if this is the best option (as there is no model of the INA2141).
I am not 100% of the proper result plot of the 1/Beta graph and I am having troubles to plot the real open loop gain of the OPA333 in order to get the frequency compensation done.
Some pictures are attached to clarify the questions.
Am I missing something or the results are the expected?
Regards,
Alberto
Hello Alberto,
If you're primarily interested in the noise and transfer function, I recommend building a discrete INA141 using ideal amplifiers and adding noise sources externally. I have created a rudimentary TINA model (attached) that seems to work pretty good with respect to noise and functionality. Please understand, however, that it uses ideal op amps. Therefore all other parameters are not modeled (e.g. offset voltage, BW, common-mode voltage, output swing, etc.). Note that I only added voltage noise sources. You may want to add a current noise source. If you do this, you can find the current noise source in TINA-TI under File->Open Examples->TI Examples->Noise Sources. Finally there is a good presentation on INA noise that can be found here:
e2e.ti.com/.../3514.instrumentation-amplifier-noise
I hope this helps. Best of luck!