电流偏置电路电流偏置VS.电压偏置引起误差电压偏置：连线寄生电阻引起IRdrop，ta,ERsRpOVrefanalog3blocklRin连线电阻对电流偏置影响很小AA,-VBRpIBRsIref西安文道大学Chpt.#5.电流和电压基准NIVEE6/54Lab of Mixed-Signal Systems
Lab of Mixed-Signal Systems 6 /54 Chpt. #5. 电流和电压基准 电流偏置电路 电流偏置 VS. 电压偏置 电压偏置：连线寄生电阻引起IR drop，引起误差 连线电阻对电流偏置影响很小 RS RP IB VB Iref
电流基准的产生简单电流产生器lOUTlouIeQQMMIgtInaVcc-VBEDDGS=1inoutR0R产生小电流需要大电阻，增大芯片面积西安文通大学Chpt.#5.电流和电压基准NIVELJAOTONC7/54LabofMixed-SignalSystems
Lab of Mixed-Signal Systems 7 /54 Chpt. #5. 电流和电压基准 电流基准的产生 简单电流产生器 CC BE out in V V I I R DD GS out in V V I I R 产生小电流需要大电阻，增大芯片面积
产生小电流的基准Widlar电流基准bipolarβF+ 1louTR2=0VBEI-VBE2βrβp +1Ic1lOUT- Vr InVrInloUTR2=0βrIsiIs2RLlouTIfβF-→00,IctIeNloUTQ1Q2VrInVrIn-loUTR2 = 0IsiIs2SR2IINVr InloUTR2lOUT西安文通大学Chpt.#5.电流和电压基准8/54Labof Mixed-Signal Systems
Lab of Mixed-Signal Systems 8 /54 Chpt. #5. 电流和电压基准 产生小电流的基准 Widlar电流基准 bipolar
INVr In=loUTR2loUTEXAMPLEInthecircuitofFig.4.31la,determinethepropervalueofR2togivelouT=5μA.AssumethatVcc=5V,R,=4.3k2,VBE(on)=0.7V,andβr-→co.5V-0.7V=1mAIiN =4.3kΩIN(1 mAVrIn=26mVIn137mV5μAToUTThusfrom(4.191)loUTR2=137mVand137mVR2= 27.4kΩ25uA西安文通大学Chpt.#5.电流和电压基准9 /54LabofMixed-SignalSystems
Lab of Mixed-Signal Systems 9 /54 Chpt. #5. 电流和电压基准
MOS WidlarVGS1-VGS2-loUTR2=0louTR2+Vo2-Vov1=0ZRlOUT22M,M2+4R2Vovlk'(WIL)2k'(WIL)2loUT2R2R2西安文通大学Chpt.#5.电流和电压基准NIVEESITLJAOTONC10/54Labof Mixed-Signal Systems
Lab of Mixed-Signal Systems 10 /54 Chpt. #5. 电流和电压基准 MOS Widlar