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Not able to understand ADA4807-2ACP's behavior

Hi

I have set up the ADA4807 in simulation as shown in the picture below and I do not seem to get the gain unlike mentioned in the article A Low Power, Low Cost, Differential Input to a Single-Ended Output Amplifier | Analog Devices

What am I doing wrong here?

Thanks

Tushar

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  • Hi Tushar,

    Computing using the formula Vout = -Gain * (Vin1-Vin2), we get Vout = 2.4Vpk-pk sine wave. This means that to output this signal we need a negative supply.

    Another solution we could do here is to level shift both opamp to 1.5V so that the output signal 2.4Vpk-pk is centered at 1.5V

    Regards,

    Mon 

  • Hi Mon,

    I have a follow up question -

    I am experimenting with a new setup where one of the inputs is negative. Please see the setup below.

    Would such a setup work reliably with no negative supply?

    What I see is that the output does respond and gains up the input but not exactly 20x as one would expect. 

    e.g. for an input of -100mV, the output is 1.97V; for -80mV, the output is 1.57V; for -40mV, it is 0.77V and for -8mV, it is 0.13V. 

    As you can see, the output is consistently less by 30mV than what one would expect it to be. What is the reason for this behavior?

    Can I reliably use this setup in an application?

    Thanks

    Tushar