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AD8338 Application note and Design Question

Question asked by sadeniji on May 24, 2016
Latest reply on Jun 20, 2016 by JinoL

Fig.1.PNGFig.2.PNGFig.3.PNGI will divide my Question into 3 parts.

No.1 is related to the fig.1 that contains the statement about the Having a filter as a short circuit with the AD8338, it says the gain becomes very large. What does that mean and h ow does an LC lowpass filter act as a short.

I have a lowpass filter that looks like the fig.2 below. Does that act like a short?

 

No.2 : In the application note http://www.analog.com/media/en/technical-documentation/application-notes/AN-1192.pdf

It is said on page 7 that the input can be filtered with Lin and Cin, please how can I calculate this value. I am designing for 1MHz system and I am using the AD8338 as an input to ADC. I will be using the AD8130 as a buffer to convert the differential signal into single ended.

 

No.3 : I have made a circuit that looks like fig.3. I would be glad if someone can advice me if it would work before I proceed with my design. I have a little doubt with my Vref connection. I am not sure if this can be connected to ground. Bye the way I am not using the AGC feature.

 

Please note that I am still in the learning phase of design and I might have asked some basic and elementary question. Kindly pardon me.

 

Thanks.

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