Transcription of W = 10 m, L= 2
1 1. MOSFET Equations a) N- channel MOSFET Cut Off ! VGS"VT ! IDS=0 Linear ! VGS>VT, ! VDS"VGS#VT ! IDS= nCoxWLVGS"VT()VDS"VDS22# $ % & ' ( (1+)VDS) Saturation ! VGS>VT, ! VDS>VGS"VT ! IDS=12 nCoxWL(VGS"VT)2(1+#VDS) The simplest model in SPICE (Level 1 or default model) uses the above equations. Parameter SPICE Parameter Units Typical Values nCox KP A/V2 200 VT0 VTO V LAMBDA V-1 b) P- channel MOSFET Cut Off ! VSG"VT ! ISD=0 Linear ! VSG>VT, ! VSD"VSG#VT ! ISD= pCoxWLVSG"VT()VSD"VSD22# $ % & ' ( (1+)VSD) Saturation ! VSG>VT, !
2 VSD>VSG"VT ! ISD=12 pCoxWL(VSG"VT)2(1+#VSD) Example) VS = 4 V, VG = 2 V, VD = 1 V VT = V, = 0, Kp = 100 A/V2 W = 10 m, L= 2 m Find MOSFET type, operation region, IDS. - Solution ! VDS>VGS"VT#saturationISD=100 210 2 (2"" )2(1+0)=360 AIDS="360 A 2. MOSFET Circuits Example) The PMOS transistor has VT = -2 V, Kp = 8 A/V2, L = 10 m, = 0. Find the values required for W and R in order to establish a drain current of mA and a voltage VD of 2 V. - Solution ! VD=VG"VSD>VSG#VT"saturationIDS=12 KpWL(VSG#VT)2(1+$VSD)=8 2W10 (3#2)2(1+0)= m,R=20k% Example) The PMOS transistor has VT = -1 V, Kp = 8 A/V2, W/L = 25, = 0.
3 For I = 100 A, find the VSD and VSG for R = 0, 10k, 30k, 100k. - Solution = 0 (no channel length modulation) ! 1)R=0VD=VG"VSD>VSG#VT"saturationISD=12 KpWL(VSG#VT)2=8 2$25$(VSG#1)2=100 VSG=2 VVSD=2V2)R=10kVD#VG=IR=100 $10k=1"VSD=VSG#VT"saturationorlinearISD= 12 KpWL(VSG#VT)2=8 2$25$(VSG#1)2=100 VSG=2 VVSD=1V3)R=30kVD#VG=IR=100 $30k=3"VSD<VSG#VT"linearISD=KpWL((VSG#VT )VSD#VSD22)=8 $25$((VSD+3#1)VSD#VSD22)=100 VSD% )R=100kVD#VG=IR=100 $100k=10"VSD<VSG#VT"linearISD=KpWL((VSG# VT)VSD#VSD22)=8 $25$((VSD+10#1)VSD#VSD22)=100 VSD%
