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sinara-hw / Urukul

4 channel 1GS/s DDS (AD9910 or AD9912 variant)
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Attenuator DC block cap #58

Closed dtcallcock closed 2 years ago

dtcallcock commented 3 years ago

There is no DC blocking cap on input of IC3.

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From IC3 datasheet:

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Was this an oversight or does the DC GND path provided by FL2+TR1 mean we don't need this (though if this is the case, you could probably make a similar argument for the output blocking cap given the next component is an attenuator that has a DC path to GND)?

gkasprow commented 3 years ago

Good point. Some switches have an internal charge pump and can work with GND-referenced signals. In our case lack of caps can induce nonliearities.

jordens commented 3 years ago

The jumper decouples.

dtcallcock commented 3 years ago

Ok, now I spot the reference to 'C28' in this comment.

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But AFAICT, C28's location or value aren't on the schematic. Can the ambiguities of the 'mystery red box' easily be fixed? If not then more clarity in the comment would help.

gkasprow commented 2 years ago

I added a comment obraz

gkasprow commented 2 years ago

I also changed the frame around components so the values will be visible in pdf