Hello Guys,
We are using AD9633 in our system, and ADA4930-2 is used as AD9633's driver. We have finished hardware design and got the PCB. Now, we are testing and debugging the board's hardware. And we found some problems of ADA4930-2.
The ADA4930-2's schematic design is as following figure:
As above figure, the unipolar analog signal is fed to amplifier’s positive input port. And there are total three connecting options for amplifier’s negative input port. We can use one of these 3 options according to actual situation.
- DC_BIAS can be used directly, this can be verified thru Diff-Amp Calculator (option 1)
- If there is no bias DC, use +3.3V connected in series thru a 330ohm resistor (option 2)
- Refer to amplifier datasheet’s figure 55, connecting to +3.3V thru 1.87K ohm resistor (option 3)
Note: above option 2 comes from ADI engineer’s suggestion, who get this idea after simulating by using LTSpice. This connection can approximately replace the bias DC. And above option 3 should only be used for bipolar input signal.
For option 1, we also confirm with Diff-Amp Calculator, as following image:
For option 2, we also simulated thru LTSpice, the simulation result as following image:
Now, we encounter problem when we test our hardware. The function generator will provide the single-ended unipolar analog input signal, as following image:
However, the ADA4930-2's output measured as following image in this case:
Above measured result is very different by comparing with LTSpice or Diff-Amp Calcualtor's simulation result. What cause this issue? We try option1 and option 2, both will get same result.
