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THS4531A: Input Signal DC Bias

Evan Cornell
Expert 1380 points
Part Number: THS4531A
Other Parts Discussed in Thread: ADC122S655, , TINA-TI

I am looking to use THS4531A as differential amplifier driving ADC122S655. The source is a high voltage sensor. I have the sensor pins connected through resistor divider to unity-gain buffer, then fed to the THS4531A inputs. 

My question is this: I have the unity-gain buffers at DC bias of 0V, whereas the THS4531A is uni-polar supply. My Tina-TI simulation seems to produce correct results, but I don't quite believe it.. can I have an explanation for why this circuit works properly?

Thanks!

  • 0
    TI__Genius 15975 points

    Hi Evan,

    While operating a fully differential amplifier (FDA) like THS4531A on uni-polar supply, the key care-about is to make sure the input pins are within the input CM voltage range as specified in the datasheet for the required output swing. The input common mode compliance is attached below for convenience.

    For THS4531A FDA with DC input of 0V, the dc value at the input pins will really be voltage division of output pins by Rf and Rg, (or Vin_CM = {Rg/(Rg+Rf)}xVout). So, as long as the THS4531A input CM compliance is met using unipolar supply and DC bias of 0V for the required output swing and Rf & Rg, the TINA-TI should not complain. It would be good if you could attach your TINA-TI schematic if there are further questions related to this.

    Best Regards,

    Rohit