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Main points of this past exam are: Beginning, Common Parameters, Values, Amplifier, Small-Signal Parameters, Transistor, Minimum Number
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EE 105 Midterm-2 Solution Prof. Ming C. Wu Spring 2007
q := 1.6 10⋅ −^19 C ni := 10 10 cm −^3 Vth :=0.026V ε 0 8.854 10⋅ −^14 F cm := εs := 11.7 ⋅ε 0 εox :=3.9 ⋅ε 0 mS := 0.001S fF := 10 −^15 ⋅F
(1) (^) g_m := 0.1mS ro := 100kΩ Cgd := 10fF Cgs := 100fF Cdb :=10fF
Rs := 1kΩ R_L :=100kΩ
(a) (^) Rout ro R_L⋅ ro +R_L := Rout = 5 × 10 4 Ω
Av := −g_m ⋅Rout Av =− 5 (c) There are 2 poles, one at input and another at output
Cin := Cgs +Cgd ⋅( 1 −Av) Cin =1.6 × 10 −^13 F Cout Cdb Cgd 1 1 Av
:= + ⋅ Cout =2.2 × 10 −^14 F ωp_in 1 Rs Cin⋅ := ωp_in 6.25 × 1091 s
ωp_out 1 Rout Cout⋅ := ωp_out 9.091 × 1081 s
(d) (^) Output pole is the dominant pole. The 3-dB frequency is
f_3dB 1 2 ⋅ π
:= ⋅ωp_out f_3dB =144.686 MHz
(2) (^) μnCox 100 μA V^2
:= μpCox 50 μA V^2
:= V_TH := 0.4V Vdd :=2V W_L1 := 10 W_L2 := 20 W_L3 := 40 W_L4 := 20 V_GS1 :=1V (a) Id1 = Id2 (magnitude) V_overdrive1 := V_GS1 −V_TH V_overdrive1 =0.6 V V_overdrive2 V_overdrive1 μnCox W_L1⋅ μpCox W_L2⋅
:= ⋅ V_overdrive2 =0.6 V
Vx := Vdd − V_TH−V_overdrive2 Vx =1 V V_overdrive3 := Vdd − Vx−V_TH V_overdrive3 =0.6 V V_overdrive4 V_overdrive3 μpCox W_L3⋅ μnCox W_L4⋅
:= ⋅ V_overdrive4 =0.6 V
Vout := V_overdrive4 +V_TH Vout =1 V
1 3 1 3 2 4 2 4
1 3 2 4
1 3 2 4
m m m m V m m m m
n ox p ox p ox n ox
(b)
Av W_L1 W_L3⋅ W_L2 W_L4⋅
:= Av = 1
(3) (^) μnCox 100 μA V^2
:= μpCox 50 μA V^2
:= λn 0.1^1 V
:= ⋅ λp 0.1^1 V
:= ⋅ Rs := 100 Ω
(a) This is a common gate amplifier. M1 is the main amplifying transitor
(b) The current going through M4-M5 can be found from the current mirror W_L6 := 10 W_L5 := 10 W_L2 := 10 Iref := 100 μA Id5 Iref W_L W_L
:= ⋅ Id5 = 100 μA
Id2 Iref W_L W_L
:= ⋅ Id2 = 100 μA
(c) The output current is equal to the input current, with opposite sign. So Ai = -
(d) (^) W_L1 := 10
Id1 := Id2 gm1 := 2 ⋅μ nCox⋅W_L1 ⋅Id gm1 =4.472 × 10 −^4 S
2 1 1 2 1 1
o m m s in in S o S m m
( ) e
vs_vin_ratio
1 gm Rs 1 gm
:= vs_vin_ratio =0.