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OPA197: Amplifying sinus signal

Dukel
Intellectual 610 points
Part Number: OPA197

Hi,

I would like to amplify a vibrations signal. A geoscope detects a ground vibration and outputs a voltage between ±28.8mV within a 10 - 100 Hz spectrum.
The Analog to digital converter that I us, has an input voltage range of ±2.56V meaning that the gain needs to be 88.889

I'm using the Analog Engineer's calculator to determine the resistor values and resulted in the following circuit:

 

unfortunately this does not amplify my input. Can anyone suggest another circuit that amplifies my ±28.8mV to ±2.56V?

Best regards,

Dukel

  • 0
    TI__Guru* 93105 points

    Hi Dukel,

    The OPA197 is completely capable of handling the task you want accomplished. The issue with your circuit is you are applying a +/-28.8 mV signal to the non-inverting input, and expecting +/-2.56 V output using a single +10 V supply. In order for the OPA197 to function correctly in a bipolar input, output application, it must be powered by a dual polarity (+/-) power supply such as +/-10 V, or using the method described in the next paragraph.

    The other method that you can use to remedy the circuit is to apply a positive dc common-mode voltage in series with the input ac signal generator. For example, if you place a +5 V dc source in series with the generator the output will be centered about +5 V. You can see a TINA simulation circuit below. The TINA file is attached.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

    OPA197_single_sply.TSC

  • 0 in reply to Thomas Kuehl
    Intellectual 610 points

    Dear Thomas,

    Thank you for your reply, I recon that I didn't place the -10v in this circuit. for some reason I removed it before I safed the image. 
    The problem was the location of the 223ohm resistor. The circuit below is what I changed.

    Thanks again!

    Best regards

    Dukel