Resistive Load 1 Let's use a resistor as the load. The region of operation of M,depends on its size and the values of Vin and R. We are interested in the small-signal gain and the headroom (which determines the maximum voltage swing). We will calculate the gain using two different methods Vout 1.Small-signal model Vop 2.Large-signal analysis o Vout VTH Vint Vin (a (b) -Voo 车Ro d 03/24 ))))
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Resistive Load -2 Gain-Method 1:Small-Signal Model o Vout (d) This is assuming that the transistor is in saturation,and channel length modulation is ignored. The current through Rp: i。=gnVx ·Output Voltage: Vum=-i。·R,=-gn·y·R。 。·Small--signal Gain: A==-g·R。 705/24
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Resistive Load -3 Gain-Method 2:Large-Signal Analysis -Voo 。 If VIN<VTH,M1 is off,and VoUT=VDD=Vps. 李RD VOUT =VDD -RD'iD =VDD Ay= OVOUT=0 OVIN a As VIN becomes slightly larger than VTH,M1 turns on and goes into saturation(Vos≈Voo>VGS-VTH≈o). 人=北-R=-见分A-C”化-gy =R4C7化-)Rg A.OV As VIN increases,Vos decreases,and Mi goes into triode when VIN-VTH=VoUT.We can find the value of VIN that makes M switch its region of operation. =-见4=形-R4C化-r=化-) 032 10
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Resistive Load -4 Gain-Method 2:Large-Signal Analysis(Continued) As VIN increases,Vos decreases,and M goes into triode. Faro-koVe-Ro-n-er 2 -%cg) OVOUT oVIN OVIN OVIN We can find A,from above.It will depend on both VIN and VouT. If VIN increases further,M goes into deep triode if VouT<<2(VIN-VTH). ar=w-风o=a么C.艺a-a)a Voo 车RD ，Vout VOUT= VDD VDD RON Vi，Rn 、=VDD'RoN+RD 1 M +RpMCa-Vm)1+Ro Ro (c) 705/24 ))) 14
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