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OPA197: OPA197: Regarding the output at the time of differential amplifier

Part Number: OPA197

Dear Thomas-san,

Thank you for your response.
I understand the contents.

However, which item in the data sheet can be understood that Vo1 and Vo2 output is clipped at about 5.77V and 230mV?

Best regards.

  • Hello user5994067,

    The OPA197 datasheet Electrical Characteristics table, under "Vo - Voltage output swing from rail" is where you would find the information. Note that it lists both positive and negative rails and different output load conditions; unloaded, 10 k and 2 k loads. You can see from the table that the more heavily the output is loaded (lower resistance), the more distant the maximum swing is from the rail. Keep in mind that the swing limits are an output saturation condition and not a linear operating condition. Therefore, to assure linear operation use the Open-loop gain parameter (Aol) swing ranges listed in the "Test Conditions" column. Swing ranges for load resistances of 2k and 10 k are provided.

    Your indicated in your previous e2e post that you are powering the OPA197 from a +6 V supply. Be aware that this is below the minimum specified supply voltage of +8 V and adherence to the limits in the table isn't assured. Also, if you are using a single +6 V supply and resistive load to ground, the output can only source current. That means that the swing limit is only applicable to how close the output will swing to the positive rail when sourcing current to the load resistor.

    Below, I show a simple TINA Spice simulation for the OPA197 positive output swing limit when it is sourcing current into three different resistive loads of 1 Meg, 10 k and 2 k. You can see from the output graph how the swing to the rail becomes more restricted as the load resistance decreases (higher output current).

    A similar simulation could be performed where the load is connected to the positive supply and the output is driven low. In that case, the output is sinking current from the load to ground.

    I hope this helps.

    Regards, Thomas

    Precision Amplifiers Applications Engineering