s55
Junior Member level 2
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I understand the MOS capacitor or the MOSCAP is used for some benefits, such as high capacitance density and more. Then, the capacitance of the MOSCAP changes with the gate voltage as explained in the C-V plot of the following link:
From the above curve, there is big difference of capacitance (e.g., ~80pF in different document) between the bottom of depletion (deep depletion) and inversion (or accumulation) region.
Here is my question. I'm trying to use the MOSCAP as the binary-weighted capacitor array (instead of using regular poly capacitors) in my charge-redistribution SAR ADC design. In my ADC, I think there shoud be serious problem that different ADC input voltages (Vin) applied across the MOSCAP array cause different capacitances of each MOSCAP as shown in the above link (e.g., 0 [V] of Vin corresponds to the depletion, while 1[V] of Vin maps to inversion region). This results in wrong binary search process. Am I correct?
If I'm correct, then how do we use the MOSCAP? Is there any specific situation only that we can use the MOSCAP, for example the MOSCAP between voltage supply and ground or something like this?
From the above curve, there is big difference of capacitance (e.g., ~80pF in different document) between the bottom of depletion (deep depletion) and inversion (or accumulation) region.
Here is my question. I'm trying to use the MOSCAP as the binary-weighted capacitor array (instead of using regular poly capacitors) in my charge-redistribution SAR ADC design. In my ADC, I think there shoud be serious problem that different ADC input voltages (Vin) applied across the MOSCAP array cause different capacitances of each MOSCAP as shown in the above link (e.g., 0 [V] of Vin corresponds to the depletion, while 1[V] of Vin maps to inversion region). This results in wrong binary search process. Am I correct?
If I'm correct, then how do we use the MOSCAP? Is there any specific situation only that we can use the MOSCAP, for example the MOSCAP between voltage supply and ground or something like this?
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