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corner analysis of the self biasing current source

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lanesu

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there is a resister in the self baising current source.And the value of the resister is very important to the current source.But the scale of the resister varies largely from different corner models,for example from 0.6 to 1.4.This results a large variation of the current.
Are there any solutions that could banish the change of the current which is due to the variation of the scale?Or I need not to take care about the change?
 

if you want very accurate current,you should trim or use external resistor.
 

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    lanesu

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Current is always = V/R.
If you want the current to be less variation over R, try to make the V has the same trend as R, so that they cancel each over corners.

Having current dependant on R may not be an issue to some designs, such as amplifier. If you have a bias current = Vref/Rref, and the amplifier having the resistor Rload same type as the Rref in the bias current, basically you still get relatively constant signal swing over corners, proportional to V/Rref*Rload, if Vref is bandgap voltage.
 

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    lanesu

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