MOSFET drain current equation with channel length modulation

[daudaudaudau]

In Sedra&Smith's microelectronic circuits they have the following expression for the drain current in a MOSFET in saturation

i_D = 1/2µ_pC_ox(W/L)V_ov²(1+V_DS/V_A)But I don't see how this can be correct. Wikipedia also has another expression, see http://en.wikipedia.org/wiki/Channel_length_modulation#Shichman.E2.80.93Hodges_model

So which is correct?

 

[NascentOxygen]

As wikipedia states, no formula accurately models a contemporary device, for this you must resort to a computer model. Nonetheless, perhaps you might find a derivation of the formula to be illuminating? :s

See http://www.onmyphd.com/?p=channel.length.modulation