Which to choose for RC low pass filter: NMOScap or MIMcap?

[patriot]

hi, i need a capacitor more than 4pF to construct a RC low pass filter, i have an alternative between NMOScap and MIMcap. Would any guys give me some advices?
which one is better?

 

[ieropsaltic]

moscap versus mim quality factor

MOScaps have higher density, i.e they can achieve much higher capacitance for same area than MIM caps. However, they're non-linear and have much lower Q factor. For a LPF, I don't think that this would affect you much (but better check the non-linearity). Also, the MOScaps require biasing to achieve the proper capacitance, so you must ensure that you apply proper bias to them.

 

[patriot]

mimcap versus moscap

MOScaps have higher density, i.e they can achieve much higher capacitance for same area than MIM caps. However, they're non-linear and have much lower Q factor. For a LPF, I don't think that this would affect you much (but better check the non-linearity). Also, the MOScaps require biasing to achieve the proper capacitance, so you must ensure that you apply proper bias to them.

yes,the MOScap density is 3.6 times larger than MIMcap, so i choose MOScap. But in different corners,the bias of the MOScap varies. should i only verify the circuit in all corners ?
BTW:Is the NMOScap fabricated on p-substrate or DNwell?

 

[raptor1981]

mimcaps

In a low pass filter where the product of capacitance and resistamce determines the total time constant associated with the circuit. So a variation will effect the rise and fall time. Hence it is better to use MIMcap than MOScap