OPA145: CM voltage range (max) acc to DS: (V+)-3.5V (?) at supply +/-2.25 V

Kalle Gronvik

Part Number: OPA145
Other Parts Discussed in Thread: OPA392, OPA397, OPA325

Acc to the datasheet the OPA145 CM voltage range (max) is (V+)-3.5V. However, the diagrams are stated at VCM = Vs/2 even for +/-2.25 V supply. I can't see how these specs are compatlible.

Can someone explain please?

4 months ago

0 Marek Lis 4 months ago

TI__Guru 62290 points

Hi Kalle,

Most OPA145 graphs are given for +/-18V supplies but for any under +/-2.25V supplies its input common-mode would be at Vcm= -1.25V so to meet the linear range of: (V-)-0.1V < Vcm < (V+)-3.5V

0 Kalle Gronvik 4 months ago in reply to Marek Lis

Prodigy 130 points

Thanks Marek,

I must say that's really disappointing.

If OPA145 can't operate in standard configurations, e g as a follower, or inverting amplifier with non inverting input to 0V with V+ < 3.5 V I think the datasheet is severly misleading when it says the device accepts down to +-2.25 V supply. At least should the datasheet include clear test circuit diagram for those cases.

0 Marek Lis 4 months ago in reply to Kalle Gronvik

TI__Guru 62290 points

Hi Kalle,

OPA145 is a high voltage part (36V) with most specifications optimized for +/-15V supplies. Even though it operates down to +-/2.25 V (or 4.5V single supply), it is not optimal for low supplies. For +/-2.25V or 5V single supply I would recommend using a low voltage part like OPA325, OPA392 or OPA397.

0 Kalle Gronvik 4 months ago in reply to Marek Lis

Prodigy 130 points

Thanks Marek, I'll check into those.

0 Marek Lis 4 months ago in reply to Kalle Gronvik

TI__Guru 62290 points

No problem, Please let me know if you have further questions.

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OPA145: CM voltage range (max) acc to DS: (V+)-3.5V (?) at supply +/-2.25 V