OPA145: OPA145 output swing

Sebastien Grenier

Prodigy 40 points

Part Number: OPA145

Hi, do you know why the U2 in this circuit does not buffer the 2,9 Volts at +5Volts on the supply (see attached)?

Thanks a lot for your help.

Sebastien

op amp.TSC

over 2 years ago

0 Sebastien Grenier over 2 years ago

Prodigy 40 points

It works well when VCC=6,5 volts and above.

0 Thomas Kuehl over 2 years ago in reply to Sebastien Grenier

TI__Guru* 93105 points

Hello Sebastien,

The OPA145 maximum Common-mode voltage (VCM) is rated at (V+) – 3.5 V. Therefore, the maximum positive VCM for a +5 V supply is +1.5 V. In the circuit schematic the VCM is +2.9 V, which exceeds the VCM limit by +1.4 V. The +6.5 V supply sets the +2.9 V input right below a now higher +3 V VCM maximum.

A different op amp having a higher positive VCM limit closer to the supply rail rating would be needed for a +5 V supply application.

Regards, Thomas

Precision Amplifiers Applications Engineering

0 Sebastien Grenier over 2 years ago in reply to Thomas Kuehl

Prodigy 40 points

Thanks a lot Thomas.

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OPA145: OPA145 output swing