MISFET threshold voltage

However, such barriers are used and are created by special technology (enhanced types of MISFET). In this case, a voltage difference between the gate and source, Uqs, lower than or equal to the positive value of the so-called threshold voltage, U-r, cannot overcome the barrier and the transistor is shut (drain current, I, is zero). On the other hand, the depleted types of MISFET have negative values of Ux and even if Uqs < 0 is applied, the current Id can flow (for Uqs > Uj). In first-order MOS transistor theory, the dependence of Id on Ugs is described by... 

Fig. 6. Dependence of drain current, on gate-source voltage, Uqs, for depletion type of n-MISFET at different temperatures. Uj, threshold voltage.

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