AN804
Vishay Siliconix
P-Channel MOSFETs, the Best Choice for High-Side Switching
Historically, p-channel FETs were not considered as useful as their n-channel counterparts. The higher resistivity of p-type silicon, resulting from its lower carrier mobility, put it at a disadvantage pared to n-type silicon. Getting n-type performance out of p-type FETs has meant larger area geometries with correspondingly higher inter-electrode capacitances. Consequently, a truly plementary pair- a p-channel and an n-channel device that match in all parameters- is impossible. Yet, despite its shortings, the p-channel MOSFET performs a vital “high-side” switch task that the n-channel simply cannot equal. Used as a high-side switch, a p-channel MOSFET in a totem-pole arrangement with an n-channel MOSFET will simulate a high-current, high-power CMOS (plementary MOS) arrangement. Although the p-channel MOSFET cannot plement the n-channel in both on-resistance and capacitance simultaneously, such binations...
