high speed dac out transfer function

[greggdaug]

dacout_sch_and_sim.png

I have been attempting to reverse engineer the components from the dac output to the sma connector using the pictures provided in:

http://www.eevblog.com/forum/microcontr ... schematic/

After measuring the dac output frequency response (scope terminated into 50 ohms), I came up with the schematic enclosed. I then used ADS to optimize the component values and obtained the enclosed results.

Can anyone comment on this? If this is close to being correct, the dac output filtering leaves a lot to be desired, especially if one is expecting a broadband 50 ohm Zout.

Thanks,

-Gregg

[Nils Roos]

Attachments seem to be still broken. Could you upload the picture somewhere and post a link, please ?

[greggdaug]

Try this:

https://github.com/greggdaug/RPsims

First performed AC sim with sin(pi*freq/fs)/(pi*freq/fs) current source to mimic dac response. Optimized filter components to match normalized voltage gain. Then performed s-parameter sim to get Zout and return loss.

If someone has access to a commercial VNA, it would be nice to get 1-port s-parameter files for both the ADC inputs and DAC outputs.

-Gregg