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[SOLVED] Should MOSFETs in a comparator be in saturation region?

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CHL

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Hello
I wonder if MOSFETs in a comparator should be in saturation region or not.
Let's say an input out of two comparator inputs is fixed at a reference voltage and the other input varies. We can check the gain and bandwidth by putting the reference voltage to the input. In this case, should I make all the TRs be in saturation? or only bias TRs?
 

Putting them in saturation helps. Near your trip point, the comparator behaves as an amplifier. The higher the gain, the lesser the transition region. To get as much gain as possible, put your devices in saturation!
 
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    CHL

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"Should be", until they can't - some positions just do
not have the headroom. For example the lower ("master")
devices of a cascode mirror are going to sit at edge of
linear/saturation because one is forced Vgs=Vds by wiring.


Rules of thumb are fine up to a point - depends where
you put the thumb.
 

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