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OPA2171

Harvey Wiggins
Prodigy 50 points
Other Parts Discussed in Thread: OPA2171

There is no current noise spec given for the OPA2171 part.  Very peculiar to me that such an important spec is left out.  Does anyone know what it is?  Is it so bad it was left off?

  • 0
    TI__Guru**** 189401 points

    Hu, Harvey,

    Welcome to e2e, and thanks for your interest in our products. Sorry for the delay, I have highlighted your post to my colleague who works on the OPA2171. 

    D2

  • 0
    TI__Guru 68531 points

    Hervey,

    The input current noise is a function of an input bias current, i²=2*q*IB*∆f, where q is an electron charge (1.6E-19) and IB is an input bias current. Therefore, for the CMOS op amps like OPA2171, with a very low input bias current (IB=8pA), the current noise spectral density is negligible.  It may be nonetheless calculated by first solving the above equation to express its value in terms of spectral density:

    i/√∆f = √(2*q*IB) =  √(2*1.6E-19*8E-12) = √(2.56E-30) = 1.6E-15 = 1.6fA/√Hz

    Thus, input current noise spectral density for OPA2171 is 1.6fA/√Hz.