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OPA690: Power rail question.

Part Number: OPA690

Can I power this OPAMP with +10V and -1V? , trying to use it to drive a load cell circuit and trying to avoid the cross over distortion by adding a small negative bias. 

  • Yes. From the OPA690's point of view, +10 V / −1 V is the same as 11 V or ±5.5 V.

  • Crossover distortion? there is no crossover in the input stage of the OPA690?

  • Hi Li,

    because the OPA690 has a rather limited input voltage range and output voltage range, the key question here is what input voltage range and output voltage range you desire.

    Kai

  • Hi kai,

    the input voltage is 0V to 1V, 

  • Hello Li, thank you for providing the input voltage of 0V to 1V. I will take a look as well. 

    Best,

    Alec

  • Maybe I didn't describe it correctly.. the main reason is we want the opamp to output true 0V when it can... when it is negative voltage input is connected to GND, it cannot output to GND.. that's why I am consider a -1V rail. 

  • Hello Li,

    Just to clarify, you need the output to be 0V, which necessitates a split supply configuration?

    The datasheet recommendation of +/- 5V supplies would correlate to a -1V and +9V supply. Since the device can accept a 12V total split supply voltage range, this configuration (and your -1V to +10V) are valid. 
    However, your common mode input range and output swing limitations will make it more difficult to achieve a 0V output on a -1V supply. 

    The minimum available output swing on +/- 5V split supplies is +/- 3.6V. The amplifier is swinging up to 1.4V from the supply rails. Knowing this, a negative supply voltage of -1.5V would be sufficient, swinging ideally up to 7.5V. You can stretch the positive supply to 10V, but your input common mode ranges and output swing available may shift due to the imbalance; the mid supply voltage shifts from 3V up to 4.25V. 

    Please look over the datasheet and provided curves to analyze the best supply configuration. If there are other design needs in addition to needing to output 0V at the output, please let me know. 

    Best,

    Alec

  • yes Li, 

    The OPA690 requires about 1.6V headroom to the supplies on the input pins

    And, depending on the load current, 1V to a a bit more on the output pins

    This comes up so often, it found its way into this recent article, 

    https://www.electronicdesign.com/technologies/analog/article/21261391/three-major-design-pitfalls-plaguing-new-analog-signalpath-designers