In accumulation mode the capacitance is just due to the voltage drop across tox.Capacitance is non-linear in depletion University of California, Berkeley.
Capacitance is depletion region is smallest.Capacitance is linear in accumulation and inversion.
Small-signal capacitance is slope of Q-V curve. In inversion, what’s the depletion region width and charge? University of California, Berkeley. The charge in the substrate (body) consist of holes: University of California, Berkeley. The entire voltage drop is across the oxide:. Calculate threshold voltage: University of California, Berkeley. In depletion, the charge grows slower since the voltage is applied over a depletion region University of California, Berkeley. In accumulation, the charge is simply proportional to the applies gate-body bias. Inversion depletion accumulation Q-V Curve for MOS Capacitor Under this condition: University of California, Berkeley. This is a good assumption since the inversion charge is an exponential function of the surface potential. A simple approximation is to assume that once inversion happens, the depletion region stops growing. Apply KCL around loop: Gate (n+ poly) + − − − − − − − University of California, Berkeley. 
For this condition, the surface potential has to equal the negative of the p-type potential.The threshold voltage is defined as the gate-body voltage that causes the surface to change from p-type to n-type.At this point, the depletion region stops growing and the extra charge is provided by the inversion charge at surface + − + + + + + + + + + + University of California, Berkeley.The surface potential increases to a point where the electron density at the surface equals the background ion density.− − − − − − − − − Body (p-type substrate) − − − − − − − − Inversion Charge has a square-root dependence on applied bias + − + + + + + + + + + + University of California, Berkeley.Potential drop across the oxide and depletion region.Positive charge on gate terminates on negative charges in depletion region.− − − − − − − − − Body (p-type substrate) − − − − − − − − Depletion: VFBp-type substrate, PMOS n-type substrate Oxide (SiO2) Very Thin! University of California, Berkeleyīody (p-type substrate) Accumulation: VGB “Metal” is more commonly a heavily doped polysilicon layer n+ or p+ layer.Sandwich of conductors separated by an insulator.Gate (n+ poly) Body (p-type substrate) MOS Capacitor I-V Curve University of California, Berkeley.
0 kommentar(er)
