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OPA192: The relationship between VCM and Vos of OPA192

Sophia Yao
Prodigy 701 points
Part Number: OPA192

Hi team,

1. When I looked at OPA192 datasheet, I found below figures, could you please explain them for me? what is the relationship among Vs, Vcm and Vos?


2. The customer's schematic is as below. The value of VCM is 12V and the positive power supply value is 16V. Actually the positive power supply value can change and the worst value tested is 14.1V. So do you think the customer's application has any risk? It is an urgent case. 

Thanks very much!

Sophia Yao

  • 0
    Guru 140200 points
    Hi Sophia,

    this is very well explained in section 8.3.6 of datasheet of OPA192. I can't do it better.

    Kai
  • 0 in reply to kai klaas69
    Guru 48395 points
    But the short answer is yes, as the supply dips down from nominal 16V you will get into the crossover region where you will see a varying degree of input offset shift. Some of the alternate parts might move that handover between input stages up closer to the supply. Kai, do you know in this kind of device which one might have that crossover closest to the positive supply?
  • 0 in reply to Michael Steffes
    TI__Guru 67971 points
    Since in order to accomodate rail-to-rail input common-mode voltage range OPA192 topology includes two input differential pairs, this means that at certain input common-mode voltage there is a transisiton from one pair to the other. The mid-point transition between N and P channel input differential pairs in OPA192 was designed to occur at the input common-mode voltage 2.2V below positive rail; thus for Vcc=18V, this means that transition happens at Vcm=18V-2.2V=15.8V while for Vcc=2.5V the transition occurs at Vcm=2.5V-2.2V=0.3V as shown on the graphs above.
  • 0 in reply to Marek Lis
    TI__Guru* 93105 points
    Hi Sophia,

    Do you have the information you needed regarding the relationship between Vcm and Vos for the OPA192? If so, please close this e2e inquiry.

    Regards, Thomas
    Precision Amplifiers Applications Engineering