EE1411EE1411EECS141EE141EE141--Fall 2006Fall 2006Digital Integrated Digital Integrated CircuitsCircuitsLecture 18Lecture 18PassPass--Transistor LogicTransistor LogicDynamic LogicDynamic LogicEE1412EECS141AnnouncementsAnnouncements No new homework this week Project phase one due on Monday Midterm 2 next Thursday Review session on TuesdayEE1412EE1413EECS141EE1414EECS141EE1413EE1415EECS141Class MaterialClass Material Last lecture Decoders Ratioed logic Today’s lecture Pass-transistor logic Dynamic logic Reading (Chapter 6)EE1416EECS141PassPass--TransistorTransistorLogicLogicEE1414EE1417EECS141PassPass--Transistor LogicTransistor LogicInputsSwitchNetworkOutOutABBB• N transistors• No static consumptionEE1418EECS141Example: AND GateExample: AND GateBBAF = AB0EE1415EE1419EECS141NMOSNMOS--Only LogicOnly LogicVDDInOutx0.5μm/0.25μm0.5μm/ 0.25μm1.5μm/ 0.25μm0 0.5 1 1.5 20.01.02.03.0Time [ns]Voltage[V]xOutInEE14110EECS141NMOSNMOS--only Switchonly SwitchA = 2.5 VBC = 2.5VCLA = 2.5 VC = 2.5 VBM2M1MnThreshold voltage loss causesstatic power consumptionVBdoes not pull up to 2.5V, but 2.5V -VTNNMOS has higher threshold than PMOS (body effect)EE1416EE14111EECS141NMOS Only Logic: NMOS Only Logic: Level Restoring TransistorLevel Restoring TransistorM2M1MnMrOutABVDDVDDLevel RestorerX• Advantage: Full Swing• Restorer adds capacitance, takes away pull down current at X• Ratio problemEE14112EECS141Restorer SizingRestorer Sizing0 100 200 300 400 5000.01.02.0W/Lr=1.0/0.25 W/Lr=1.25/0.25 W/Lr=1.50/0.25 W/Lr=1.75/0.25 Voltage [V]Time [ps]3.0•Upper limit on restorer size•Pass-transistor pull-downcan have several transistors in stackEE1417EE14113EECS141Complementary Pass Transistor LogicComplementary Pass Transistor LogicABABBBB BABABF=ABF=ABF=A+BF=A+BB BAAAAF=A⊕ΒÝF=A⊕ΒÝOR/NOREXOR/NEXORAND/NANDFFPass-TransistorNetworkPass-TransistorNetworkAABBAABBInverse(a)(b)EE14114EECS141EE1418EE14115EECS141Solution 2: Transmission GateSolution 2: Transmission GateABCCABCCBCLC = 0 VA = 2.5 VC = 2.5 VEE14116EECS141Resistance of Transmission GateResistance of Transmission GateVout0 V2.5 V2.5 VRnRp0. 0 1. 0 2. 00 10 20 30 Vout, VResistance, ohmsRnRpRn || RpEE1419EE14117EECS141PassPass--Transistor Based MultiplexerTransistor Based MultiplexerAM2M1BSSSFVDDGNDVDDIn1In2SSSSEE14118EECS141Transmission Gate XORTransmission Gate XORABFBABBM1M2M3/M4EE14110EE14119EECS141Delay in Transmission Gate NetworksDelay in Transmission Gate NetworksV1 Vi-1C2.52.500Vi Vi+1CC2.50Vn-1 VnCC2.50InV1ViVi+1CVn-1VnCCInReqReqReqReqCC(a)(b)CReqReqCCReqCCReqReqC CReqCInm(c)EE14120EECS141Delay OptimizationDelay
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