Study of the Characteristics and Non-Ideal Effects of Mosfet and Jfet

Abstract

In this article, we study Metal–Oxide–Semiconductor Field-Effect Transistor (MOSFET) and Junction Field-Effect Transistor (JFET). The fundamental physics and characteristics of MOSFET and JFET have been considered. In Chapter 1, we discussed MOSFET structure, energy band diagram with p-type and n-type substrate, threshold voltage, Origin of Subthreshold CMOS Design and Capacitance-Voltage Characteristics. Both the N-channel and p-channel MOSFET with enhancement mode and depletion mode were described. We have considered the ideal C–V characteristics of the MOS capacitor and deviations that occur from these idealized results in practical situations. There are three operating conditions of interest in the MOS capacitor: accumulation, depletion, and inversion.Subthreshold region is defined as when the supply voltage is less than the device threshold voltage. The energy saving and operation of the subthreshold circuit is demonstrated, and its advantages are discussed here. In chapter 2, we discussed JFET characteristics, the transconductance model, JFET as switch, JFET channel pinched-off, N-channel, and p-channel JFET, biasing of JFET, operation of JFET, ideal dc current-voltage relationship—depletion mode JFET, velocity saturation effects, subthreshold, and gate current effects. This three-terminal semiconductor device can be electronically used as controlled switches, amplifiers, or voltage-controlled resistors. The JFET may wear out if the gate is positively biased. Three non-ideal effects, such as channel-length modulation, velocity saturation, and subthreshold current are considered. Each of these effects changes the ideal current-voltage relationship.