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Bandgap MOS Mismatch (MonteCarlo)

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wturtle

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Hey guys,

I have a problem here I could use a few suggestions.
I building a current mode bandgap, the one that uses resistor divison to provide sub-1v voltages.

My circuit behaves good in typical (0.3% variation over VT) and around 2.6% at all corners.
The problem is the montecarlo simulations. The devices mismatch introduce a lot of error, putting nearly 200mV variation at my output (nearly 20%).

The bigger sources of my problems are the PMOS mismatch for the current mirror and opamp offset (nearly 10mV).
Do you guys know any techniques for compensating mismatches or offset at the opamps?
Maybe a self calibrating resistor that adjusts at the power up?

Thanks,
 

Using larger ( by maintaning W/L ratio) will reduce the mismatch.So larger MOS area has less mismatch..
 

That's the easy way out xD. I read about chopping for ampop. Is it a good solution? I've read that it can reduce the offset to virtually nothing atfer low pass filter
 

Make sure that the current mirrors have adequate Vgs-Vth and Vds-Vdsat margins.
Say about 100mV or so. That will help a lot with mismatch.


Chopping can help you get rid of the Op-Amp offset.
 

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