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OPA2333: About change of input noise.

Genius 5945 points

Replies: 7

Views: 90

Part Number: OPA2333

Hi team.

I'd like to know about the input noise accuracy.
The input noise is typ value.
Is there Min and Max value as a reference value.

If you don't have it, I'd like to know what the Max/Min is likely to be.

My customer is having trouble with input noise and they suspect it is the cause.


Sincerely.
Kengo.

  • Hi Kengo,

    what noise level is he observing?

    Often noise is a demodulation of EMI. Then HF low pass filtering can help a lot. Can you tell more about the project? Can you share a schematic?

    Kai

  • In reply to kai klaas69:

    Hi Kai.

    Thank you for your reply.
    I understood about EMI noise.

    However, I'd like to know the amount of noise in the amplifier itself.


    Sincerely.
    Kengo.

  • In reply to Kengo.Y:

    Hi Kengo,

    I think there are no min max values available.

    Kai

  • The typical total integrated input voltage noise for OPA2333 max noise bandwidth (G=1) is 48uVrms - see below - but this does not include current noise (it depends on the input impedance) and the noise from the external passive components like resistors and EMI/RFI.

    As a rule of thumb, the broadband noise may vary over process variation up to +/-30% while 1/f noise may double from its typical value.  Thus if your customer uses the OPA2333 in a buffer configuration, its total noise is dominated by the broadband noise and a max variation of 30% from its typical value would translate into ~+16% increase in total noise from the value simulated above.

    Marek Lis, MGTS
    Sr Application Engineer
    Precision Analog - TI Tucson

  • In reply to Marek Lis:

    Good info Marek, and again a schematic would help a lot to make sure we are not chasing the wrong issue. 

    Also, 1/f doubling from typ value? Perhaps, at least on a chopper like the OPA2333 there is no 1/f noise. 

    Michael Steffes

  • In reply to Michael Steffes:

    Micheal,

    Yes, that is true that you do not need to worry about 1/f input voltage noise in chopper amplifiers BUT because of the IB spikes coming from the chopping action of the front-end switches, you need to worry much more about conversion of those current spikes across the source and/or input resistance into voltage spikes that may result in a large input offset voltage error in configurations with unmatched input impedances.

    Marek Lis, MGTS
    Sr Application Engineer
    Precision Analog - TI Tucson

  • In reply to Marek Lis:

    All the more reason to start with the schematic on these types of questions

    Michael Steffes

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