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OPA2140 Linearity Data

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: OPA2140, OPA140

Hello,

Are there the linearity data(Vin vs Vout data) at the Gain =1 and -1 of OPA2140?
The customer request the actual sample data. (Simulation data is not acceptable.)

Best Regards,
Ryuji Asaka

  • 0
    TI__Guru 67971 points

    Ryuji,

    We do not specify op amp linearity per se but one may back-calculate it from datasheet information.  Since in gain of -1, the linearity will be a function of Vos change with the change of Vout (input common-mode voltage is fixed), one may use AOL minimum spec to extract the maximum Vos variation; for RL=10k and Vs=+/-18V, the minimum AOL is specified to be 120dB at 25C, thus as the output changes +/-17.65V (350mV from either rail), the Vos may vary by maximum +/-17.75uV.  Since in the G=-1 Vos gets multiply at the output by the noise gain of 2, the effective linearity for G=-1 for RL=10k is 114dB (or 0.0002%). Likewise, for RL=2k at 25C, min AOL  is 114dB, which translates into linearity of 108dB or 0.0004%.

    In the gain of +1, Vos changes due to the input common-mode voltage, Vcm (CMRR), and output Vout (AOL) variation.  Since the minimum CMRR at 25C is 126db while the min AOL for RL=10k 120dB, the overall linearity for G=+1 would translate in the worst case into [(0.000001)^2+0.0000005^2]^.5=0.00000112 or 0.000112% (using vector addition since CMRR and AOL are NOT correlated).  Note of caution: all of the above calculations apply only to linear operation of OPA140; thus (V-)+0.35V<Vout<(V+)-0.35V and (V-)-0.1V<Vcm<(V+)-3.5V

  • 0 in reply to Marek Lis
    Guru 20090 points
    Hi Marek,

    Thank you for the reply.
    Could you please share the application note , equation or any document if there is for my understanding?

    Best Regards,
    Ryuji Asaka
  • 0 in reply to Ryuji
    TI__Guru 67971 points

    Ryuji,
    I don't have an application note to share to explain non-linearity calculation but all the information you need to calculate the non-linearity were given in my previous post. You just need to understand what non-linearity really represents in case of op amp in a follower configuration. If there was no variation of Vos with the change of the input signal, Vout would perfectly follow Vin and non-linearity would be 0. However, since for G=1 Vout=Vin+Vos and gain is equal to delta_Vout/delta_Vin = (delta_Vin+delta_Vos)/delta_Vin, the non-linearity is thus defined by delta_Vos/delta_Vin; thus if Vos changes by 1uV per 1V change in Vin (120dB), the non-linearity will be 1uV/1V =1e-6 or 0.0001%, etc.  Also, keep in mind that AOL=delta_Vout/delta_Vos while CMRR=delta_Vin/delta_Vos.  Since in G=-1 Vin=constant, delta_Vos= delta_Vout/AOL.  In case of G=1, both Vin and Vout change, thus the total delta_Vos is a vector addition of delta_Vout/AOL and delta_Vin/CMRR.