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INA500: AMC3311-Q1 and INA500A

MAIDEEN AKBARALI
Prodigy 50 points
Part Number: INA500
Other Parts Discussed in Thread: INA500

Tool/software:

Hi,
In differential to single ended amplifier I am getting 25usec of delay between inpu and output. could you please tell is it advisible to use the same?. If not please suggest alternatives?. Please find the attached images (VHV and V single_ended ) for more information. 

Thanks and Regards,

Abdul.

  • 0
    TI__Mastermind 33483 points

    Hello Abdul,

    What you are seeing is the overload recovery time of the device. This is the amount of time for the amplifier to exit saturation and return to a linear operating range. This is caused because your ideal output voltage is below your negative supply rail. The transfer function for the INA500A is ((IN+) - (IN-))*G + REF = Vout. In this case, G = 1, so it will just be (IN+) - (IN-) + REF = Vout.

    When the amplifier stays within the linear operating range, there is no input delay.

    When shifting the input square wave to bring IN+ 100mV below V-, you can now see the delay.

    There are multiple ways to address this. Do you need to have a linear output when IN- is greater than IN+?

    Best,
    Gerasimos

  • 0 in reply to Gerasimos Madalvanos
    Prodigy 50 points

    Hi Gerasimos,

    I am a bit confused by what you said "This is caused because your ideal output voltage is below your negative supply rail."

    The "ideal output voltage" (you mean the output voltage of the diff amp?) should not swing below VEE, which is set to ground. The expected output voltage switch will be between 0-2V, because the differential input voltage will be in that range.

    For a 3.7V power single supply rail and a maximum differential input voltage of +2V, am I exceeding the linear operation range of the INA500A?

    Is there any way I can send a simulation file for you to take a look at?

  • 0 in reply to MAIDEEN AKBARALI
    TI__Mastermind 33483 points

    Abdul,

    You should be able to send me a simulation by clicking Insert > Image/video/file, then clicking "upload". Please see below for the photos.

    Best,
    Gerasimos

  • 0 in reply to Gerasimos Madalvanos
    Prodigy 50 points

    AMC311_V1.TSC
    Hi Gerasimos,
    Please find the attached simulation file. Requesting to take a look and revert. 

    Thanks and Regards,
    Abdul

  • 0 in reply to MAIDEEN AKBARALI
    TI__Mastermind 33483 points

    Hello Abdul,

    I have created an ideal amplifier model in your circuit to show with no supply limitation, what your output should mathematically be. Before the output is supposed to go to 2V, the ideal output is 336uV. This is outside the linear output range of the INA500 is 8.5mV per the datasheet. This is why you are seeing the overload recovery delay, as the amplifier is not in a linear operating range.

    You can avoid this by adding a small positive bias to your difference amplifier output.

    Best,
    Gerasimos