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4th order high pass filter with low noise

Question asked by dhhsieh on Aug 1, 2017
Latest reply on Aug 2, 2017 by Matt.Duff

Dear Analog Devices team,

I am designing a 2-stage, 4th order high pass filter with an overall gain of 1 and source impedance of 5 ohms. My application is low noise.
After doing some research, I chose the Sallen-Key architecture and Butterworth type and used the Filter Wizard to pick the lowest noise configuration I could. The diagrams for input impedance, circuit and noise are attached.
My first question is impedance matching. If my source impedance is 5 ohms, a filter input impedance of 50 ohms will be an issue, right?
My second question is, is it a good idea to use the AD797 for this application? I wanted to make sure.

That is all for now. Thank you in advance.

Daniel

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