PGA855: Correct input circuit with single ended input signal and single supply

Hi Dominik,

I'm assuming you will want to connect the single-ended voltage to the positive terminal input terminal, and connect a 7.5 V DC voltage to the negative input terminal.  This will give you +/- 7.5 V of differential voltage swing.  However, for the input voltage range on the PGA855, the voltage at either input (Vin+ or Vin-) must be lower that 2.5 V from the positive rail and higher than 2.5 V from the negative rail:

So, 15 V on the input, with the supply at 15 V won't work.  There is no way around this unless you:

1) Increase the supply voltage to 17.5V 
2) Attenuate the signal before the PGA with a resistor divider
3) AC-couple the inputs, if the input is an AC signal.

Let me know if any of the 3 situations above can be used and we can go from there.

Regarding the valid input range, we do have a calculator that shows the valid input/output ranges depending on how each is configured:

https://www.ti.com/tool/download/PGA85X-INPUT-OUTPUT-RANGE-DESIGN-CALC

Once we get some more info. then we can proceed from there.

Regards,
Mike

Hi Mike,

Thank you very much for the quick response.

I have noticed this with the input voltage range and this is not a problem as my signal that oscillates around 7.5V does not exceed 10Vpp.
I was just not quite sure about the wiring of the negative input terminal and that's why I asked.

Exactly, I connect my signal to the positive input terminal and a DC voltage of 7.5V to the negaitve input terminal.

Thanks for the help!

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