Question

_{5. Consider the n-channel D-MOSFET amplifier circuit. Ipss and Vp vary in the ranges shown due to manufacturing variations VDD 12V 5 MS2 330 2 10 HF C1 sig 100 2 0.1 uF RL 1 kS2 10mA s lpss 12 mA -2.5V Vp s-1.5V s GS 1 ΜΩ 250Ω 22 uF Find the resulting variations in Id, gm, and Av. (Hint: you can consider four cases, which make use of the extreme values of Ioss and Vp. This can be done by plotting four device curves, and this can be done easily using Excel, Matlab, or some other computer tool.) You may assume that the resistors are fixed in value}

Answer 1

"Given 10 MA: lessthanorequalto I_DSS lessthanorequalto 12 MA -2.5 v lessthanorequalto rD lessthanorequalto -1.5 v For finding we go for DC - analysis {capacitor rightarrow open circuit where V_fn = 12 v (1 M ohm/(1 + 5) m ohm = 2 v Req = 5 M ohm Vertical-bar Vertical-bar 1 m ohm = 5/6 m ohm I_D = I_DSS = (1 - V_GS/VP)^2 V_GS = V_fn - I_D (RS) V_GS = 2V - I_D (250) \r\n = partial differential I_D/partial differential vgs = 2 I_DSS/V_P (1 -V_GS/VP) = 2 I_DSS/V_P squareroot I_D/I_DSS g = 2 squareroot I_D DSS/VP AC - equipment R"" L = R'L Vertical-bar Vertical-bar RDS tildeequal R'_2 = 248 ohm = 0.248 k ohm v_0 = -RL"" gn vgs voltage across Req = vgs and voltage across Req is also given by voltage division rule. \r\n v_s times 5/6 m ohm/((10^-4 + 5/6) m ohm approximatelyequalto v_s vs = v_gs voltage gain AV = v_0/v_s = -R""_L gm vgs/vgs AV = R""_L gm when I_DSS = "