Benefits of cascoding

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swagata

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somewhere i found that major benefits of cascoding are

1. increases Rout & since gain=GmRout so by cascoding voltage gain increases.

what benefits it's having for current-mode?
2.it shields the Vds variation due to channel length modulation.
This point is not clear to me.
plz explain the logic & giving related formulas.Also send lecture notes & papers if available.
 

refer to this post for more on current mode
 

1)actually not only does the voltage gain increase but also the output impedance decreases and also the output swing gets reduced....

2)the Vds variation is locked by the MOS above which fixes the Vds to a particular value and hence avoiding channel length modulation....
 

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    swagata

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the vds of low device changes little
 

it also eliminates coupled feedforward path from input to output
 

dis adv : stack transistor increases so supply voltage is need to increases to make proper bias.
not suitable for low voltage operation .
 

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