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AMC1301: Not getting 8.2 Gain

Balaji TS2
Intellectual 270 points
Part Number: AMC1301
Other Parts Discussed in Thread: AMC0311D, AMC0330D

Hello,

We are using AMC1301 to amplify our input volatge, as this amplifier has fixed gain of 8.2. But in practical testing, AMC1301 is amplifying only 4 times instead of 8.2 times.

I am attaching our schematics screenshot. Please let us know is there any issue in our design.

image.png

To verify how how much gain we are getting from AMC1301, we have taken readings at C753(input of AMC1301) and C1747(output of AMC1301). For example, If we are getting 100mV at C753 means, at C1747 we are getting only around 400mV.

Is our design correct? What might be the issue?

Regards,

Balaji

  • 0
    TI__Expert 6370 points

    Hi Balaji,

    The voltage between VOUTP-VOUTN should be 8.2 times your input voltage of 100mV.  Across C1747, you are measuring across a voltage divider of R736, R734, and R2310 that is dividing the voltage in half.  What is the purpose of your R2310 resistor?

    Also, this device is intended for current sensing applications.  It has a lower input voltage range and a low internal impedance.  The low impedance will cause gain errors when you try to measure across a high impedance resistor instead of a low value shunt resistor.

    I would recommend moving to one of our voltage sensing parts.  We have recently released the AMC0311D/R/S and AMC0330D/R/S devices for voltage sensing applications.  They come with a single-ended and ratio-metric output version also, which would remove the need for the INA you are using for differential to single ended conversion.

    Thanks.