Question

(25pts) 3. For a four resistors n-channel JFET, find the operating points (VGS, ID, and VDs). Assume Ipss = 5mA, Vp= -4.5V and IG-0 Given: Vpp = 12 V, Ri=2M.2, R2= 1.5M2, RD=6 k2, Rss = 4k12, (25pts) 4. Design a four resistors n-Channel JFET bias circuit for the following specificatio YTT -

Answer 1

Given Four resistors n-channel JFET + Vop Tass=5mA , Vp = -4.5V IGRO Ri ID VID=12v; R = 2m2 Vin but Vth R2=1.5M, Ro=6652 ! Vs Rz ERS Rss = 4ka Biasing Network Find Vas, Ip and Vos R2 Valong th= VOD Rth = Roll Rz (2x1.5) - ms 2+1.5 = 3 = (2475) 2 Valor) th= 3.5 1.5 3.5 X 12 Rth = 0.857 m 2 Valor) vih 5.143 V VG = 5.143v Vs = VG-VGS Vs - 5.143-VGS ID Vs Rs VG-VGS Io = Rs

Io 5.143 - Vas UXIO² Drain Current in active region ID= Ioss Pour You 2 5.143- VAS vp 3 4x10² Ioss (1-vas 5x16"[- Vis ] (-4.5) 5.143-VGS 4x10² 20 + vas] = 5:143 - Vas 2084.5+ Vas 5.143-VGS 20.25 20[20:25+ q vast vash] = 104.146 - 20:25 Vgs 405+180VGS tzvęs = 104-146 20-25VGS 200GS +180 Gs+ 20.25 VGS+ 405-104.46=0 20VGS + 200-25 s + 300.54=0 VG -1.838 ; VGs = -8.174 VGS For n-channel JEET Vas is usually negative and Vass Vp (-8.174 -4.5) | VG5 -8.174 ID = VG-VGS 5.143 - (-8.174 Rs 4X103 5.143 +8.174 4X103 In = 3.329 810 = 3.33MA -3

Vos = vo Vs Vo=? Vs = VG-Vas VDD-VD Io = = 5.143-(-8.174) RD 50143+8.174 3.33810 -3 12-VD 6x103 Vs = 13.317 19.98 = 12-VD Vo = 12-19.98 VD = -7.98 VDS 13•317 = -7.98 -21.297 = Vos 2 -21.3 v Vos= -21.30 ID = 3.33mA VGS =-8.174 V

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