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About PGA2500

Other Parts Discussed in Thread: PGA2500

hi sir:

About PGA2500, I have aquestion to ask.

It is that when I try to adjust PGA2500 level shift to support the AD input range 0~5.

But it is not work.   I am not sure that I control is corrected or not.

Links are described in detail below:

https://goo.gl/MfrGGE

My application describe as below :

Microph phone + INA110 + PGA2500 + AD7988

AD7988 is single end input, so I want to adjust PGA2500 level shift to match AD7988 input range 0~5v

Thanks.

Best Regards,

Kun You Lin

  • Hello,

    What is your desired PGA2500 common-mode voltage, +2.5V? The schematic only shows a connector on the VcomIN pin. You must remember that the VcomIN pin sets both the input and the output common-mode voltages of the PGA2500. Since you have Vin- shorted to GND, you are directly connecting (VcomIN - 0.65V) to GND which will cause short-circuit currents inside the part and most likely cause severe performance issues.

    As specified in p. 13 of the PGA2500 data sheet, setting VcomIN = +2.5V causes output swing limitation and THD+N degradation. As an alternative, we propose keeping VcomIN = 0V and AC-coupling the PGA2500 output as shown in Figure 8.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps