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sinara-hw / Phaser

Quad channel 1GS/s RF generator card with dual IQ upconverter and dual 5MS/s ADC and FPGA in EEM form factor
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power budget: OPA2197 #109

Closed hartytp closed 3 years ago

hartytp commented 3 years ago

there are two sets of OPA2197. Both are listed as being supplied from +-11V5 in the power budget, which is not correct

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gkasprow commented 3 years ago

good catch, fixed

dnadlinger commented 3 years ago

As a minor detail, also seems like those feedback resistors are unnecessary, or at least unnecessarily large, on the reference buffers.

gkasprow commented 3 years ago

they match the resistance visible by the positive opamp input

dnadlinger commented 3 years ago

But the OPA197 bias current is 20 pA max., so they only serve to increase voltage noise for little benefit? (Not worth touching at this point, of course.)

gkasprow commented 3 years ago

in this case, you are right.