最新场效应管放大电路17461幻灯片.ppt
场效应管及其应用场效应管及其应用4.1 Field-Effect Transistors Two types: junction field-effect transistor(JFET) and the metal-oxide-semiconductor FET(MOSFET)。 4.1.1 Junction Field-Effect Transistors(结型场效应管)1. Structure and Operation(结构及工作） 1) Basic Structure and Symbol(基本结构及符号) 4.1 场效应管场效应管场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用场效应管及其应用 4.1.2 Metal-oxide-semiconductor FETs(绝缘栅型场效应管绝缘栅型场效应管) 1. Enhancement-mode MOSFET(增强型绝缘栅场效应管增强型绝缘栅场效应管) 1) Structure and Symbol(结构及符号)sgdNNP型硅衬底衬底引线gdsgds(a)(b)(c)SiO2 4.1 场效应管场效应管Structure of N-channel enhancement-mode MOSFETSymbol of N-channel enhancement -mode MOSFET (a) Symbol of P-channel enhancement -mode MOSFET场效应管及其应用场效应管及其应用2) Characteristics(特性)（1） Transfer Characteristic of N-channel Enchancement-mode MOSFET when uGSUT,2) 1(UuIiTGSDOD （2） Drain Characteristic of N-channel Enchancement-mode MOSFET 4.1 场效应管场效应管场效应管及其应用场效应管及其应用4321iD / mA02468uGS / VuDS10 VUGS(th)3 V012345iD / mA6 V5 V4 V3 V24681012141618uDS / V(a)(b) （a） Transfer Characteristic （b） Drain Characteristic 4.1 场效应管场效应管UT场效应管及其应用场效应管及其应用sgdNNP型硅衬底衬底引线gdsgds(a)(b)(c)Structure of N-channel depletion-mode MOSFETSymbol of N-channel depletion-mode MOSFET (a) Symbol of P-channel depletion-mode MOSFET 4.1 场效应管场效应管 2. Depletion-mode MOSFET场效应管及其应用场效应管及其应用 N-channel depletion-mode MOSFET（a） Transfer characteristic （b） Drain characteristic5 4321024681012uDS= 常数uGS / ViD / mAUGS(off)IDSS02468101214162 V1 V3 VuGS= 2 V1 V24681012uDS/V(a)(b)iD / mA0 VWhen uGS UP, 2)1 (UuIiPGSDSSD 4.1 场效应管场效应管Up场效应管及其应用场效应管及其应用4.2 FET AmplifiersvThe common-source amplifiervThe common-drain amplifiervThe common-gate amplifier 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用The common-source JFET amplifierSmall-signal JFET parameters constant uiuigGSDuDSgsdmDefine transconductance as: 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用 iD uG S iD uGS ID SS UP 0 Q Calculate gm algebraically and graphically)1(2UuUIgPGSPDSSm 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Small-signal model of JFET g mugs u gs G D S id rd ttancons iuivrDDSuSGddsd 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用A common-source JFET amplifier with fixed bias +VDD RD VGG vd s id RG + - vs C 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用The small-signal equivalent circuit RD rd RG g m vg s vgs G D S id + vs - vd s 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Example The JFET in the amplifier circuit has IDSS=12mA,VP=-4V,and rd=100k. 1. Find the quiescent values of ID and VDS. 2. Find gm. 3. Draw the equivalent circuit. 4. Find the voltage gain. +15V 2.2k -2V vd s id 1M + - vs C 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Solution:t.counterpar BJT its from obtained becan ich an that whsmaller th generally isamplifier JFET a from obtainablegain voltage the* 5 . 6)10100/102 . 2(103/ 4. youeself.by draw . 31031234)12(2 . 24 . 8)2 . 2)(3(15 3)42 1 ( )(12) 1 ( . 1333322rRgvvASmAmAVmAgVkmARIVVmAmAVVIIdDmsdsvmDDDDDSDSSDPGS 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Bias-stabilized JFET amplifiers vds +VDD RD RS R1 R2 + - vs 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Self-biased JFET amplifier vds +VDD RD RS RG + - vs 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Example The JFET has transconductance 4000S at its bias point. Its drain resistance is 100k. Assuming small-signal conditions, find the overall voltage gain, VL/VS. VL +20V 4k 500 1M 2.2M + - VS 10k 12k + - 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Unbypassed source resistor vds +VDD RD RS R1 R2 + - vs 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Common-drain amplifier VL +VDD RS R1 R2 + - VS rs RL + - 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Example The JFET in the circuit has gm=510-3S and rd=100k. Find 1. the input resistance; 2. the voltage gain. VL +24V 1.5k 1.8M 470k + - VS 10k 3k + - 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Solution:0.81 )3|5 . 1|100(1051)3|5 . 1|100(105 107 .3727 .372 )|(1)|( . 27 .372)470(|)8 . 1 (| . 13321kkkkkkkRRrgRRrgrrrvvkkMRRrLSdmLSdmsininSLin 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Common-gate amplifier +VDD RS + - VS rs VL RD RL + - 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Small-signal MOSFET amplifiers For depletion-type MOSFET, the parameter of small-signal model is identical to the parameter of JFET small-signal model. For enhancement-type MOSFET:) 1(2 constant UuUIuigTgsTDODSmGSDu 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用A common-source NMOS amplifier VL +VDD RD RS R1 R2 + - VS rs RL + - 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Example The MOSFET shown in the circuit has the following parameters: VT=2V, =0.510-3, rd=75k. It is biased at ID=1.93mA. 1. Find the input resistance. 2. Draw the small-signal equivalent circuit and find the voltage gain VL/VS. VL +18V 2.2k 500 47M 22M + - VS 10k 100k + - 4.2 场效应管放大器场效应管放大器场效应管及其应用场效应管及其应用Solution:.922 )100|2 . 2|75(104 . 1 101515 )|( 104 . 1)278. 4(105 . 0 78. 4)500)(93. 1 ( 18472222 . 215)22(|)47(| . 133321kkkKMMRRrgrrrvvSVVgVmAMMMRIVVMMMRRrLDdmsininSLmSDGGSin 4.2 场效应管放大器场效应管放大器34 结束语结束语
