Noise bellow 0.5V with OPA380

Frederico Lima

Other Parts Discussed in Thread: OPA380

Hello you all!

The schematic bellow shows the transimpedance amplifier which I have been using. The OPA380 is the operational amplifier in this case. I can not understand the reason that bellow 0.5V a 56KHz oscillation shows up and it disappears when the signal reaches almost 0V. Would it help to solve the problem if I use a supply voltage of -5 and 5V instead of GND and 5V? What could be the reason of this oscillation? I have checked if there could be some external influence but that doesn't seem to be the case.

Thanks for the attention!

over 14 years ago

0 Moshe Avigdor over 14 years ago

TI__Expert 3680 points

Hello,

To get 0v at the out pin the OPA380 need Rp to Neg 5v (page 10 Data sheet)

Did you try to add it?

Best regards

Moshe

0 Frederico Lima over 14 years ago in reply to Moshe Avigdor

Prodigy 100 points

Thanks Moshe!

I thought the solution would be to apply a negative signal to the pin 4 (V-) but not -5V once the maximum voltage supply 7V is. So, I was thinking about connecting +5V to pin 7
(V+) and something like -1.4V to V-.

I have not try it yet but I will post the result here when it is done.

Best wishes,

Frederico

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Noise bellow 0.5V with OPA380