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PGA280 single-ended input, differential output

Helmut Forren
Mastermind 6805 points

Other Parts Discussed in Thread: PGA280, TINA-TI, PGA281

I just want to make sure my brain is not installed backward today.

I should be able to push a single-ended input into the PGA280, right?  Just connect INN1 to ground and INP1 to my signal.  I see common-mode rejection ratio vs frequency that's above 100dB when below 1kHz.  My need is below 1kHz and a final SNR above 60dB, going in and out of the PGA280.  So it seems to me that any common mode signal leaking through to the output will be much smaller than the SNR of the signal passing through anyway.

I'd also like to use it as a single-ended to differential converter.  My input in fact varies from +Vin to -Vin, relative go GND, and having a dual supply.  So more specifically, I believe one would call it a single-ended bipolar input.  I believe the PGA280, wired with INN1 to GND and INP1 to my +Vin to -Vin signal, will convert that single-ended bipolar input to a differential output, right?

Thanks very much.

  • 0
    TI__Mastermind 27715 points

    Hello Helmut,

    As long as you have the proper dual supply rails for the PGA280 input stage (VSP, VSN), you can definitely use the device as you've described in a single-ended to differential configuration. CMRR should be at least 120dB below 1kHz, across all gain settings.

    I've attached a TINA-TI circuit which you can use to evaluate the analog performance of the PGA280. This circuit uses the PGA281 SPICE model, but both devices contain the same analog core. The difference between them is only on the digital control side.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps

    PGA281 SE to Diff.TSC
  • 0 in reply to Ian Williams
    Mastermind 6805 points

    Great.  Thanks for the TINA-TI circuit as well.  I've already been simulating the earlier stages, and was planning to simulate this one as well.

    Furthermore, I need...

    Rather than asking, I just looked and find the TINA-TI model at http://www.ti.com/product/PGA281/toolssoftware .  In parallel, I will be using other pga's, and having found this one, I'm sure I can find the others too, and don't need to ask you for them.  Just wrote this paragraph to clear my thoughts as well as point out to future readers.