OPA990: Asymmetric power supply

Part Number: OPA990

Tool/software:

The datasheet of OPAx99 specify the power supplies of ±20 V or 2.7 V to 40 V.
I would like to use the amplifier:

- with an asymmetrical supply of +5 V and -25 V, and

- in the inverting amplifier configuration with the negative input pin within the recommended input voltage range and the positive input pin connected to 0 V.

I don't see any issue, but can TI please confirm that this asymmetric supply works with chip as well?

Thank you!

  • Js,

    In general with op amps, using a non-symmetric supply is not an issue.  You are correct to look at the common mode range as a way to confirm that this configuration is not a problem.  The OPAx990 is a rail-to-rail op amp.  Thus in your case the common mode range would be -25.2V to +5.2V because the common mode will extend 0.2V beyond the rail.  In an inverting configuration, with Vin+ at GND Vin- will be at 0V as well.  This is well inside the common mode range so you are ok.  Of course, your output swing will also be limited to approximately -24.7V to +4.7V (depending on the load).

    Best regards, Art

  • Many thanks for the prompt reply!