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Hi,
I am currently testing a THS4541 to drive the input of the ADS41B49 ADC.
The input is DC coupled and I am using the recommended circuit specified in the THS4541 datasheet (Figure 80, page 47)
The issue I am having is that when I connect anything at the input, the THS4541 "pulls up" the signal a couple of hundreds mV. For instance when I apply a Sinewave of +-500mV reference to zero, the reference changes to approx 150mV. IT gets back to zero when I disconnect it. Is this behavior expected? Any pointer of what could causing it? The Protection diode perhaps?
The only difference I see between the circuit in the datasheet and my implementation is that the ADS41B49 has a1.7V Vocm instead of a 0.95V. Could that be the cause?
Thanks in advance for your help
Hi Kai,
Thanks for your answer.
Sorry, I was not clear enough. What I mean is that the sine is nt over zero anymore but it has a DC offset of 150mV.
Edit:
A couple of images to clarify:
Output of a Waveform generator connected directly to the Oscilloscope:
Output of a Waveform generator connected to the Oscilloscope and to the THS4541 with a "Tee junction":
Kind regards,
Thanks for the answers. I can see now why is this offset happening. In principle, there should be no offset seen by the ADC. We are still working on the software implementation to be able to evaluate it properly.
Thanks again