Hi,

There is a small nonlinear component even in linear caps such as poly-poly or metal-metal, which is important when designing very precise analog circuitry. Typically, the nonlinearity is much less than 100 ppm/V.

Intuitively, I would expect the nonlinearity to be quadratic, i.e. C(V) = C0 + C2(V^2), as I would imagine that the polarity of the applied voltage has no (or very little) influence on the nonlinearity, and only the magnitude matters. However, I often see a linear term here, and

C(V) = C0 + C1(V) + C2(V^2)

The linear term appears to be not insignificant. Why would there be a linear term at all?

Regards,
Vivek

Hi Vivek,

I'm just guessing, but since usually the parasitics on the cap bottom plate is different from the one on the upper plate  I would tend to think the sign  of the applied voltage might be important. If that was the case then it makes some sense to have a non-insignificant linear term in the capacitor model as a function of the applied voltage...

Regards
Tosei