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REF5025: 1/f noise

Kuramochi Tadahiko
Guru 28715 points
Part Number: REF5025

Hi,

REF5025 outputs DC signla(=0Hz).

However, 1/f noise is infinity at 0Hz.

How should we consider about 1/f noise of reference voltage?

Best Regards,

Kuramochi

  • 0
    TI__Genius 10951 points

    Hi Kuramochi

    If you see noise density plot of any semiconductor device, it will look as follow - 

    As graph shows , low frequency noise is always proportional to 1/f . From the graph we can conclude that value of low frequency noise depends on FC and K.

    where k = white noise (v/rt hz)

    FC is cutoff frequency for flicker noise

    The rms noise can be calculated by area measurement by taking care of Y axis unit (V/r hz ).

    So 1/f noise means the slope is inversely proportional to frequency but it doesn't go to infinite. Its final value depends on white noise and flicker noise cutoff frequency. 

     


    Regards

    Trailokya

  • 0 in reply to Trailokya Rai
    Guru 28715 points

    Trailokya-san,

    Thank you for your reply.

    >The rms noise can be calculated by area measurement by taking care of Y axis unit (V/r hz ).

    This is logarithm scale, right?

    I think that it cannot be calculate because start point of x axis is not 1Hz but 0Hz.

    > Its final value depends on white noise and flicker noise cutoff frequency. 

    What does "cutoff frequency" mean?

    Best Regards,

    Kuramochi

  • 0 in reply to Kuramochi Tadahiko
    TI__Genius 10951 points

    Hi Kuramochi San 

    FC is the frequency at which the noise start rising as you can see in the earlier diagram.It is a figure of merit.

    In logarithmic scale . start point can be some 10^-N {where N is an integer} but it is not defined at 0. 

    RMS noise contribution for <0.1Hz frequency noise is not significant because X axis is very small. 

    So the flicker noise is calculated from 0.1Hz to 10Hz usually. 

    Regards

    Trailokya

  • 0 in reply to Trailokya Rai
    Guru 28715 points

    Hello Trailokya-san,

    Thank you for your reply.

    >because X axis is very small. 

    I can not understand it. Could you please explain in detail?

    Best Regards,

    Kuramochi

  • 0 in reply to Kuramochi Tadahiko
    TI__Genius 10951 points

    Hi Kuramochi SAN

    I mean to say variation of frequency (X Axis variation) will be very small from frequency upto 0.1Hz. Hence when  you calculate integrated noise for the frequency less than 0.1Hz , that will be very small. So we calculate flicker noise from 0.1HZ to 10Hz in general.

    Regards

    Trailokya