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OPA2991: Recommended Voltage on V+ & V- Supply pins

Ahamed Faize
Intellectual 260 points
Part Number: OPA2991

Hi team,

We are planning to use OPA2991 part in our design.

For this part, we understand that VS= (V+) - (V-) is 40V. But we would like to confirm what is the max Positive and Negative voltages allowed at V+ and V- pins?


As an example : Can we connect V+ = 35V and V- = -5V. Here anyways VS = 40V. But whether V+ will tolerate this voltage?
If we use this OPAMP as Amplifier, then to generate +35V at the output, can we use this OPAMP with V+ = 35V and V- = -5V?

Please clarify.

Regards,

Ahamed Faize

  • 0
    Guru 243910 points

    This device does not have a GND pin. So it does not matter where between V− and V+ you have a voltage that you call "GND". The inputs and the output can accept and generate any voltage between V− and V+.

  • 0
    TI__Genius 15410 points

    Hi Ahamed,

    In addition to what Clemens said, the output swing capabilities are dependent on the output current. Please see Figure 6-14 and 6-15 in the OPA2991 datasheet. With no output current the output voltage will be able to get within 10mV of V+.

    Thank you,

    Tim Claycomb

  • 0 in reply to Tim Claycomb
    Intellectual 260 points

    Thanks for the inputs.

    From the above discussion, We have concluded below

    1) V+ pin can be supplied up to +40V(max). In that case, V- will be 0V. So that Vs = (V+) - (V-) = 40 V (max)

    2) V- pin can be supplied up to -40V (min). In that case, V+ will be 0V. So that Vs = (V+) - (V-) = 40 V (max)

    Please confirm our understanding.

    If the above is correct, then If we apply V+ = 35V and V- = -5V, What will be the maximum (Pk-Pk) output swing voltage (Is it (0V to 40V) or (-5V to 35V)?

    Thanks,

    Faize

  • 0 in reply to Ahamed Faize
    Guru 243910 points

    The output can swing between V− and V+. It does not matter how you choose to label the voltage at these pins.

  • 0 in reply to Ahamed Faize
    TI__Genius 15410 points

    Hi Ahamed,

    Yes your understanding is correct.

    Using 35V and -5V supplies the output swing will be from 35V down to -5V minus the output swing to rail limits of the device which is dependent on the output current of the device.

    Thanks,

    Tim Claycomb