Slide điện tử từ trường lecture 9 mosfet circuits

Lecture 09 MOSFET Circuits Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Topic • Small signal equivalent circuit model – π model – T model – Body effect • Signal stage MOSFET Amplifier – CS Amplifier – CD Amplifier – CG Amplifier Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Small-signal equivalent-circuit model gm ≡ ∂id ∂vGS k 'n W (vGS − Vt ) 2L k' W id if v gs , and vBS > ⇒ Vt ↑⇒ iD ↓ v gs < , and vBS < ⇒ Vt ↓⇒ iD ↑ Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt 10 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Fixed current Bias k 'n W gm = (VGS − Vt ) L ro = VA ID k 'n W (VGS − Vt ) 2L 2L × I − Vt = k 'n W I = ID = VGS 11 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Exercise 4.30 k 'n W (VGS − Vt ) 2L 2L × I − Vt = = × × = k 'n W I = ID = VGS k 'n W gm = (VGS − Vt ) = 1×1 = L VA 75 = = 150k ro = m ID 12 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Single stage MOS amplifiers • Common source Amplifier • Common source Amplifier + Source resistance • Common Drain Amplifier • Common Gate Amplifier 13 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt 14 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt CS Amplifier DC voltage source short DC current source open Capacitor short Replace transistor by small signal equivalent model 15 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt vo = − g m v gs (ro // RD ) RL = ∞ vo = − g m v gs (ro // RD // RL ) vi = v gs Av = − g m (ro // RD // RL ) io RL = ii = = − g m v gs Rout vs =0 = (ro // RD ) V = v gs I= v gs RG Rin = RG v gs RG Ais = − g m RG CuuDuongThanCong.com 16 Microelectronic circuit by meiling CHEN https://fb.com/tailieudientucntt CS Amplifier with source resistance 17 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt vs AC Rs g m v gs vi + v gs vo − RG vi + v gs RG RL RD RS vo Av = ii = RS RD − g m RD + g m RS RL = I − = − g m v gs RD vi = v gs + vs = v gs + g m v gs RS io g m v gs RL = ∞ vi V Ais = = − g m v gs RG = v gs (1 + g m Rs ) RG − g m RG (1 + g m Rs ) v gs = − g m v gs Rs Q − g m Rs ≠ ∴ v gs = Ro vi =0 = RD Ri = RG 18 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt G vi i = + v gs − RG i i gm I I RD RD V S RS i = g m v gs = I + I RD v gs = −iRs = −( I + I RD ) RS I + I RD = g m v gs = − g m ( I + I RD ) RS ⇒ (1 + g m RS ) I = −(1 + g m RS ) I RD ⇒ I = − I RD V Ro = = RD I 19 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt CG Amplifier vo RL = ∞ = − g m v gs RD vi = −v gs Av = g m RD io = − g m v gs RL = ii = − g m v gs vs AC Rs g m v gs vi S − RD v gs + vo Ais = RL G 20 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt vs Rs vi i gm vo i AC vi RL RD g m v gs S − + I RD v gs Ri = gm V G Ro vi =0 = RD 21 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt CD Amplifier vo RL→∞ Av = io vs AC Rs RG vi i vo gm i ro RL = ro ro + gm vi ro ro + RL = gm =i i[ro + ] v v gm g ii = i = = RG RG RG Ais = RG ro + gm = RG g m + ro g m 22 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt vs AC Rs vo vi + v gs RG − ro g m v gs RL vo RL → ∞ = ro g m v gs vi = v gs + vo = v gs + ro g m v gs ro g m Av = + ro g m Ro vi = = (ro // g1m ) io RL = = g m v gs v gs + ro g m v gs vi = ii = RG RG Ri = RG Ais = RG g m + ro g m 23 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Summery & comparisons Avo = − g m (ro // RD ) CS Amplifier Ais = − g m RG Rout vs =0 = (ro // RD ) Rin = RG − g m RD Avo = + g m RS − g m RG Ais = (1 + g m Rs ) Ro vi =0 = RD Ri = RG 24 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt CG Amplifier Avo = g m RD Ais = Ro = RD vi = Ri = gm CD Amplifier ro g m Avo = + ro g m RG g m Ais = + ro g m Ro vi = = (ro // RD ) Ri = RD 25 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt ...Topic • Small signal equivalent circuit model – π model – T model – Body effect • Signal stage MOSFET Amplifier – CS Amplifier – CD Amplifier – CG Amplifier Microelectronic circuit by meiling... gs = − g m ( I + I RD ) RS ⇒ (1 + g m RS ) I = −(1 + g m RS ) I RD ⇒ I = − I RD V Ro = = RD I 19 Microelectronic circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt