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INA166: 1uV 300kHz signal to be amplify for DAQ with minimum noise.

VIKAS MISHRA
Prodigy 20 points
Part Number: INA166

Need Help!

i am using IC INA 166 for hydrophone which has 10pf capacitance with frequency range 270kHz to 330kHz and input voltage level is 1uVpp.

what should i do for impedence matching so i can proccess aforementioned signal to be 1mVpp at low noise density.

  • 0
    TI__Expert 6250 points
    Hi Vikas,
    Using the INA166, you'll need to convert the current/charge output of the hydrophone back to a voltage to be amplified. For this application, a simple resistor across the hydrophone outputs (that is, between the two inputs of the instrumentation amplifier) should provide work. This resistance, combined with the hydrophone capacitance, will affect the low-frequency cutoff of the circuit. Based on the 10pF and 270kHz you list above, this resistor would need to be at least 60kΩ.

    Since the INA166 has significant input bias current, I'd recommend splitting this input resistor into two 30kΩ resistors in series with their midpoint tied to ground (or mid supply). This will provide a DC path for the bias current, preventing the inputs from floating to the rails.

    This is all rough estimation. If you model your hydrophone more accurately (capacitance, series resistance, etc.), you may find different values than I calculated above.

    Regarding noise, what constitutes low noise for your application?

    More information on piezo interfaces can be found here: www.ti.com/.../sloa033a.pdf