反相器及CMOS反相器性能分析.

2020/1/4第5章MOS反相器MOS反相器的基本概念及静态特性电阻型反相器E/EMOS反相器E/DMOS反相器CMOS反相器工作原理CMOS反相器的静态特性CMOS反相器的瞬态特性MOS反相器的设计三态反相器2020/1/4一、MOS反相器的基本概念及静态特性输出=3.3v3.3V输入=0v输入=3.3v输出=0v3.3V电流OUTPUTINPUT0110OUTPUTINPUTINPUTOUTPUT1.MOS反相器基本概念2020/1/4VOHVOL1outindVdV1outindVdVVout=VinVinVoutVILVIHVMVOH:输出电平为逻辑”1”时的最大输出电压VOL:输出电平为逻辑”0”时的最小输出电压VIL:仍能维持输出为逻辑”1”的最大输入电压VIH:仍能维持输出为逻辑”0”的最小输入电压VM（逻辑阈值）:输入等于输出电压传输特性2020/1/4VOHVOLVILVOHVIHVOL噪声最大允许电压噪声最小允许电压2020/1/4高噪声容限低噪声容限不定区VIHVIL10VOHVOLVNMHVNMLGateOutputGateInputVNML=VIL-VOLVNMH=VOH-VIH2020/1/4二、电阻负载型反相器VDDRLVIN=VGSVOUT=VDS1.VIN=VOL≈0V时N管截止VOUTRLVDDVOUT=VDD驱动管负载2020/1/42.VIN=VOH≈VDD时N管导通,可将MOS等效为可变电阻RMOSVDDRLVIN=VGSVOUT=VDSVDDRLIRVOUTRMOSDDLMOSMOSOUTVRRRV若RLRMOS则VOUT≈02020/1/4电阻负载型反相器电压传输特性VDDRLVOUTVINVINVOUTRL增大2020/1/4输入输出关于负载电阻的讨论INPUTOUTPUT为了使反相器的传输特性好R负载驱动在驱动管开关断开时，负载电阻相对于开关的电阻足够小在驱动管开关闭合时，负载电阻相对于开关的电阻足够大MOS晶体管的导通电阻随管子的尺寸不同而不同，通常在K欧数量级，假设它为3K欧，负载电阻取它的10倍为30K欧，用多晶硅作负载电阻时，如多晶硅的线宽为2微米的话，线长需为2mm。占面积很大，因此通常用MOS管做负载2020/1/4nninout介绍饱和MOS负载反相器Vds=VgsVgs-Vth只要开通，则工作在饱和区VIN0VOUT=VDD-VTHL当VGS=VDD-(VDD-VTHL)=VTHL时负载管关断驱动管截止VINVDD驱动管非饱和导通,负载管饱和导通22)()(21)(21THLOUTDDLoxnTHLGSLoxnDSLVVVLWCVVLWCI]21)[()(]21)[(22OUTOUTTHIDDIoxnDSDSTHIGSIoxnDSIVVVVLWCVVVVLWCI)(21THLDDmImLOLVVggVTHLDDOHVVV为使VOL接近0，要求gmLgmI有比电路三、E/EMOS反相器2020/1/4E/EMOS反相器电压传输特性VINnnVinVoutgmL/gmI减小VDD-VTVoutVin2020/1/4采用耗尽型，VGS=0时,一直工作处于导通状态VIN0VOUT=VDD驱动管截止VINVDD驱动管非饱和导通,负载管饱和导通22)(21)()(21TDDoxnTDGSDDoxnDSDVLWCVVLWCI]21)[()(]21)[()(22OUTOUTTEDDIoxnDSDSTEGSEEoxnDSEVVVVLWCVVVVLWCI)(22TEDDRTDOLVVKVVDDOHVV有比电路nninoutMEMDDoxnEoxnRLWCLWCK)()(三、E/DMOS反相器2020/1/4KR增大nninoutVDDE/DMOS反相器电压传输特性2020/1/4由PMOS和NMOS所组成的互补型电路叫做CMOSC：complementaryVinVout四、CMOS反相器已成为目前数字集成电路的主流2020/1/4CMOS反相器工作原理VinVout当输入电压Vin为高电平时，PMOS截止，NMOS导通，Vout=0当输入电压Vin为低电平时，PMOS导通，NMOS截止，Vout=VDDVOL=0VOH=VDD在输入为0或1（VDD)时，两个MOS管中总是一个截止一个导通，因此没有从VDD到VSS的直流通路，也没有电流流入栅极，因此其静态电流和功耗几乎为0。这是CMOS电路低功耗的主要原因。CMOS电路的最大特点之一是低功耗。2020/1/4CMOS反相器的传输特性VDS=VoutVinVout-VGS=VDD-Vin-VDS=VDD-VoutVGS=VinNMOSVinVtn截止▉Vin-VtnVout饱和▉▉Vin-VtnVout非饱和▉▉PMOS(VDD-Vin)-Vtp截止▉(VDD-Vin)+VtpVDD-Vout非饱和▉▉(VDD-Vin)+VtpVDD-Vout饱和▉▉VinVout0VDDVDD(1)(2)(3)(4)(5)N截止P非饱和N饱和P非饱和N非饱和P饱和N非饱和P截止VtnVDD＋VtpVinVout＋VtpVDD+VtpVinVout＋VtpVinVout＋VtnVtnVinVout＋Vtn2020/1/4CMOS反相器的几个重要参数VOHVOL1outindVdV1outindVdVVout=VinVinVoutVILVIHVM2020/1/41.VIL的计算VILVIHVIN=VILVinVout0VDDVDD(1)(2)(3)(4)(5)N截止P非饱和N饱和P非饱和N非饱和P饱和N非饱和P截止VinVout-VGS=VDD-Vin-VDS=VDD-VoutVGS=Vin1outindVdV1outindVdV对Vin求导，得PNRKKK)])(()1)(()|)(|[(2)(2inoutoutDDoutDDinoutTPinDDPTNinNdVdVVVVVdVdVVVVKVVK1inoutdVdV1inoutdVdV令，且Vin=VIL,得由（1）（2）式联立可求得VIL(2)RTNRDDTPoutILkVkVVVV12N管工作在饱和区,P管工作在线性区22)(])()|)(|(2[TNinNoutDDoutDDTPinDDPVVKVVVVVVVK(1)2020/1/42.VIH的计算VILVIHVIN=VIHVinVout0VDDVDD(1)(2)(3)(4)(5)N截止P非饱和N饱和P非饱和N非饱和P饱和N非饱和P截止VinVout-VGS=VDD-Vin-VDS=VDD-VoutVGS=Vin1outindVdV1outindVdV对Vin求导，得|)|(2]))([(2TPinDDPinoutoutoutinoutTNinNVVVKdVdVVVdVdVVVK1inoutdVdV1inoutdVdV令，且Vin=VIH,得由（1）（2）式联立可求得VIHN管工作在线性区,P管工作在饱和区22|)|(])(2[TPinDDPoutoutTNinNVVVKVVVVK（1）RTNoutRTPDDIHkVVkVVV1)2(（2）2020/1/4CMOS反相器的逻辑阈值VDDVINVMVinVout-VGS=VDD-Vin-VDS=VDD-VoutVGS=VinN管和P管均工作在饱和区22|)|()(TPinDDPTNinNVVVKVVKRRTNTPDDMKKVVVV1令VM=Vin得2020/1/4逻辑阈值与晶体管尺寸的关系1001010.80.911.11.21.31.41.51.61.71.8MV(V)Wp/Wn0.25um晶体管VDD=2.5vPMOS大NMOS大2020/1/4CMOS反相器的噪声容限RTNoutRTPDDIHRTNRDDTPoutILkVVkVVVkVkVVVV1)2(12IHOHHOLILLVVNMVVNM例考虑一个具有如下参数的CMOS反相器电路：22/40,/100,7.0,6.0,3.3VAKVAKVVVVVVpnTpTnDD计算电路的噪声容限2020/1/4解:对于CMOS反相器来说,VOL=0V,VOH=3.3V2120.73.31.50.570.7112.5outTpDDRTnILRoutoutVVVKVVKVV当VIN=VIL时,nMOS管工作在饱和区,pMOS管工作在线性区则有:22)(])()|)(|(2[TNinNoutDDoutDDTPinDDPVVKVVVVVVVK22)6.071.057.0(100])3.3()3.3)(7.071.057.03.3(2[40VoutVVVoutoutoutVILVIHVinVout0VDDVDD(1)(2)(3)(4)(5)N截止P非饱和N饱和P非饱和N非饱和P饱和N非饱和P截止1outindVdV1outindVdVVinVout-VGS=VDD-Vin-VDS=VDD-VoutVGS=Vin2020/1/420.660.056.650outoutVV20.050.0540.666.6520.660.054.1920.66Vout123.143.17outoutVVVV3.14outVV0.570.711.08ILoutVVV2020/1/420.660.056.650outoutVV20.050.0540.666.6520.660.054.1920.66Vout123.143.17outoutVVVV3.14outVV0.570.711.08ILoutVVV2020/1/4(2)13.30.72.5(20.6)1.431.7112.5DDTpRoutTnIHRoutoutVVKVVVKVV当VIN=VIH时,nMOS管工作在线性区,pMOS管工作在饱和区则有:22|)|(])(2[TPinDDPoutoutTNinNVVVKVVVVK22)7.017.143.13.3(40])6.017.143.1(2[100outoutoutoutVVVV1.17VILVIHVinVout0VDDVDD(1)(2)(3)(4)(5)N截止P非饱和N饱和P非饱和N非饱和P饱和N非饱和P截止1outindVdV1outindVdVVinVout-VGS=VDD-Vin-VDS=VDD-VoutVGS=Vin2020/1/422)7.017.143.13.3(40])6.017.143.1(2[100outoutoutoutVVVV004.294.661.22outoutVV61.2204.261.2494.694.62＋－outVV93.2V27.021outoutVVV27.0outVV55.117.143.1outIHVVV75.155.13.3V08.1IHOHHOLILLVVNMVVNM2020/1/4CMOS反相器的瞬态特性瞬态特性决定了电路的开关时间和工作速度2020/1/4CMOS反相器的瞬态特性2tttPHLPLHpd1.延迟时间tpd(传播时间）2.上升时间tr3.下降时间tf2020/1/4CMOS反相器的下降时间tfVin=VDD饱和区VinVout1.VOUT从90%VDD下降到VDD-VTHN管的VDSVGS-VTH,工作在饱和区02)VV(KdtdVCTNDDNOLOTNDDNLdV)VV(KCdt2