Question on biasing basic differential amplifier

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horacepoon

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For the most basic single ended differential input amplifier with one current source and two active load, both the current source (MOSFET) and active loads (also MOSFET) are required to be biased for expected dc current as I see in text books. Say for example, the current source is to be designed to sink 20uA and the active loads will have to be biased to source 10uA each. And all of these transistors are designed to be working in saturation region.

Can any one tell me the practical impact if the fabricated chip have small variations on the Vth of these MOSFETs? It seems to me that the variation could lead to drive the transistors out of saturation region.

Thanks,
Horace
 

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