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schematic

simulate this circuit – Schematic created using CircuitLab

I am putting together my schematic and I am trying to figure out if I can use the AD8475 as a single ended output buffer. AD8475 Found here: http://www.analog.com/en/products/amplifiers/adc-drivers/fully-differential-amplifiers/ad8475.html

My setup has 4 incoming wires (3 signals with a common gnd) going into 3 separate AD8475's. I then have 4 inputs into my ADC and I would like to have 3 signals all with a common ground again. This is very similar to the example in the AD7176-2 datasheet but is single ended with 3 buffers rather than differential with two. ADC7176-2 found here: http://www.analog.com/en/products/analog-to-digital-converters/ad-converters/ad7176-2.html

In the schematic/datasheet it only talks about differential output. Could I tie all OUT- terminals of the 3 Buffers together and then add a 10ohm resistor before the ADC and capacitors across from all the OUT+'s to the OUT- as in the fully differential mode?

My reason for using the Buffer (AD8475) is I need a VOCM so I can adjust the reference to 2.5V as well as scale down the input precisely.

Any suggestions or help would be great.

UPDATE: added schematic. Also the inputs to AD8475 will be scaled down to <5Vpp but it will be offset by the 2.5V reference voltage so it will be from 0V-5V.

looking at the AD8475 there is also some interestingly placed capacitors, and I am guessing those will have to be adjusted as well..

I also found this http://cds.linear.com/docs/en/design-note/dn473f.pdf which is specifically focused on using TI differential amplifiers as single ended ones. They seem to indicate all that needs to be done is not connect the out-, which doesn't make sense to me....

Thanks,

scarlson

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  • \$\begingroup\$ It seems pretty silly to use this part with single ended signals, while wanting a single ended output. \$\endgroup\$ – Matt Young Mar 8 '16 at 18:58
  • \$\begingroup\$ @MattYoung I agree, but is it possible? I already use that chip so I have plenty. Is it going to degrade the signal if I just tie the - low? \$\endgroup\$ – scarlso9 Mar 10 '16 at 23:13

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