Simulating AD8333

Hello, My questions are actually basic. I am using AD8333 in my project for bioimpedance measurement. The main aim is to study the food quality using 4 electrode method (auto balancing bridge method). So I wanted to use AD8333 to extract real and imaginary parts of impedance. But I am not getting any proper waveform, its completely distorted. And I wanted to know what would be the relation between the amplitude of output voltage after AD8021 and the impedance value, I am facing some difficulties in understanding that from datasheet. I hope I can use this IC for my particular application. Moreover, I am simulating in Multisim, where I cannot find any LVDS driver so I have used another LNA for LO inputs. Will it be okay? And mainly, I need your help to know if I have made some mistakes with connections or if there are any errors you can rectify for me. Kindly guide me. In my simulation for now, I have used a simple RC parallel circuit to represent bioimpedance in food samples. I am also attaching the picture of the waveform I am getting. Sorry for the circuit being a little messy.

attachments.zip
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  • 0
    •  Analog Employees 
    on Nov 5, 2015 11:34 PM


    Hello,

    Thank-you for the email. We like to receive AD8333 inquiries as it is such a specialized part that it's nice to know that people find it of interest.

    Unfortunately your schematic is very small and I think not enough digital resolution to enlarge for better visibility. Since your question involves a simulation, (I don't have access to Multisim) I cannot build and test the circuit to determine if I can improve the quality of your results. At first glance my sense is that you may have a version with limited node capacity, or you may be running a low resolution transient analysis which would be problematic. If you want to see this through you might see if the circuit solution has converged by looking for the correct dc values on the pins.

    The main question though is why use the AD8333 for a single channel application when it was designed for diversity receiver applications where parallel a plurality of channels are made coherent for signal clarity? If you just need  a single channel I/Q-demodulation there are many to be found on our product selection website. I'm not conversant with these products but you can take a look at the website and get in touch with our central applications group through this forum.

    I hope this helps,

    js

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  • 0
    •  Analog Employees 
    on Nov 5, 2015 11:34 PM


    Hello,

    Thank-you for the email. We like to receive AD8333 inquiries as it is such a specialized part that it's nice to know that people find it of interest.

    Unfortunately your schematic is very small and I think not enough digital resolution to enlarge for better visibility. Since your question involves a simulation, (I don't have access to Multisim) I cannot build and test the circuit to determine if I can improve the quality of your results. At first glance my sense is that you may have a version with limited node capacity, or you may be running a low resolution transient analysis which would be problematic. If you want to see this through you might see if the circuit solution has converged by looking for the correct dc values on the pins.

    The main question though is why use the AD8333 for a single channel application when it was designed for diversity receiver applications where parallel a plurality of channels are made coherent for signal clarity? If you just need  a single channel I/Q-demodulation there are many to be found on our product selection website. I'm not conversant with these products but you can take a look at the website and get in touch with our central applications group through this forum.

    I hope this helps,

    js

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