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I am wrapping my head around this for a bit and I understand both effects (Channel Length Modulation, Drain Induced Barrier Lowering).

While CLM is usually explained as effective decrease of the channel length due to increased depletion region, DIBL is usually explained as reducing Vth due to the same effect ("drain is a second gate").

However, fundamentally I cannot see a difference between them. Both effectively reduce the channel length due to larger depletion at the drain and hence result in finite ro. Change in Vth is just an alternative interpretation.

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In my understanding the difference is mainly in the outcome, rather than in cause. In that point of view, they are just different aspects of the same thing.

Channel Length Modulation (CLM) is due to the by the depletion region shortened channel. Higher VDS results in a shorter effective channel.

Drain Induced Barrier Lowering (DIBL): due to the by the depletion region shortenend channel, there are fewer mobile charge carriers, hence a smaller gate voltage is enough to balance their electric field. The higher VDS is, the lower Vth become.

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  • \$\begingroup\$ Hmm, are you able to still elaborate on the exact differences? If not due to the cause, due to the outcome? Do I understand correctly that the outcome of CLM is reduced output resistance (decreased intrinsic gain)? And the outcome of DIBL is not so much lower output resistance but lower Vth which means the device becomes more leaky but faster? \$\endgroup\$
    – divB
    Commented May 4, 2020 at 18:49
  • \$\begingroup\$ @divB Yes, you understand it correctly. That's it. gds vs Vth change. \$\endgroup\$
    – Horror Vacui
    Commented May 5, 2020 at 19:06

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