Threshold voltage is a very importa

Threshold voltage is a very important parameter in Mosfet, when the voltage on the gate reaches a certain value, MOS devices start to produce conductive channel, this voltage is called on voltage is the threshold voltage. Mos fet is a metal-oxide-semiconductor structure of devices, it can actually be seen as a capacitor, the electrolyte of this capacitor is silicon dioxide, the two Poles are gate metal (or polycrystalline) layer and silicon surface layer, respectively, when a voltage is applied between a metal and a semiconductor, the two opposite surfaces of the semiconductor produce an equal amount of charge with opposite polarity. In the case of the NMOS transistor, for example, the energy band on the semiconductor surface bends upward as the VG rises, and the semiconductor surface from the majority of the carrier depletion state into a small number of carriers strong inversion state, when we call Mos tube open, the size of this voltage can be expressed as: .