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AD8397 output

Hi ADI Engineer,

Recently, I encountered a unexpected problem when used the operation amplifier AD8397.Before described the problem, please see the attach file that is circuit schematic.

the range of the output is 0-10V(4*Vin)

When the Vin was less than 0.25V, the output was always low, and not equaled to 4*Vin. That means the output can not reach to less than 1V.

As soon as the negative power(Pin.4 of AD8397) changed to -3V or used another IC(TI: LM7322), the output can be able to reach to less than 1V. the circuit can achieve design requirement(output:0-10V).

My problem is that,

1, the negative power is GND, and why output cannot reach to less than 1V. From the datasheet, the output of swing is -11.83V at the condition of negative power -12V.I think that the output is about 0.2V at the condition of GND. so the output was 0.2-10V, but the actual result is 1-10V.

2,Anyway, as I described that, Can ADI engineer point out how the problem is or give some comments

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  • Hi,

    AD8397 is "rail-to-rail" output but not rail-to-rail input. The amplifier's input voltage range is ~1V from the supply rails. Means that the amplifier can only accept voltage levels within this range. Beyond this, the amplifier output would be limited by the IVR (Vout = Gain * IVR) until of course, the Output Swing limitation takes over.

    Regards,

    Jino

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  • Hi,

    AD8397 is "rail-to-rail" output but not rail-to-rail input. The amplifier's input voltage range is ~1V from the supply rails. Means that the amplifier can only accept voltage levels within this range. Beyond this, the amplifier output would be limited by the IVR (Vout = Gain * IVR) until of course, the Output Swing limitation takes over.

    Regards,

    Jino

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