- Example 11 3 An N Channel Gaas Mesfet Has 0 88v N 10 7cm A 0 25pm L Lum And Z 10um Given 5000cm V S 1 (55.21 KiB) Viewed 18 times
EXAMPLE 11.3 An N channel GaAs MESFET has = 0.88V, N, = 10'7cm, a = 0.25pm. L = lum, and Z = 10um. Given , = 5000cm/V-s and e, = 13.1, determine: a) The pinchoff voltage; b) The threshold voltage and the type of device c) The drain voltage at saturation for Va = 0; and d) The drain current at saturation for VG = 0. Solution (0.25)2 x 10-8 x 1.6 X 10-19 x 1017 a) V. = aqN/28 = 4.31V 2 X 13.1 X 8.85 X 10-14 b) V,= Vbi - V, Vi = q -9(Ec-EP) n=N) = Nexp -(Ec - E)/KT From Table 3-3, N for GaAs is 4.21 X 10''em, So that 1017 = 4.21 x 1017 -(Ec - Ep)/KT At T = 300K, (EC - Ep)/q = 0.37V From Eq. (11.10), V = 0.88 - 0.377 Vi = 0.842 and V, = 0.842 - 4.31 = -3.467V. It is a depletion-mode device. P bi