EVAL-CN0343-EB1Z RX Output Gain & Power Issue

Hi Jack,

I was reading the circuit note and I found the reference that you made above.  One thing to note is that the numbers you highlighted (132, or 42.4 dB) are not including the ADCMP670, but all the stages before that comparator.  Now if you read a few paragraphs back the author walks you through the different stages of amplifier section and even tells you the individual gains of the various filters and amplifier sections. 

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The calculated gain of each stage at 40 kHz is as follows:

 C10/R6, HPF: 0.696

 U8A, LPF: 20.4

 C16/R10, HPF: 0.691

 U8B, LPF: −19.4

 C30/R15||R17: 0.694, C31/R16||R18: 0.701

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But if you simply multiply those numbers together like stated, the math works out to somewhere around 93 (which isn't 132).  The one thing that I didn't include was the effects for the transducer itself which may be the missing piece of information here, either that or I am likely missing something as well.

One thing you could do is try and model this circuit in LTspice and see what the overall gain is, to make sure there isn't any error in the CN0343.  If things look alright, try to see if modelling the parameters of the transducer accounts for the differences in gain.  Unfortunately, this is an older design and the engineer who created/authored this is no longer around, so in order to figure out that statement, there is going to need to be some troubleshooting done.

BTW, do you have a physical board in hand?

Hi,

I believe that the question has already been answered so I am temporarily closing this thread. In case there are additional questions, feel free to reply to this thread. Thank you!

Regards,
Paul