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Berkeley ELENG 42 - Lecture Notes

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1Copyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003EECS 42 Introduction to Electronics for Computer ScienceAndrew R. NeureutherLecture # 16 Logic with a State Dependent DeviceS&O pp. 593-595, 604-606 (read for graphs and not physics or equations), plus Handout of these viewgraphs.A)State Dependent Device IOUTvs. VOUTB) Load Line Analysis for Logic LevelsC)Voltage Transfer CharacteristicsVTC = plot of VOUTvs. VIND) 42S_NMOS Pull-Down Device and Logichttp://inst.EECS.Berkeley.EDU/~ee42/Copyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003Game Plan 03/31/03Monday 03/31/04R Welcome back plus HW#8 coachingR State Dependent Devices (Transistors)R Load Line, VTC, Pull Down Device (42S_NMOS)Wednesday 04/02/03:R Pull-Up Device (42S_PMOS)R VTC and VMIDNext (11th) Week:R Monday: 4/7/03 Logic Dynamic via Switched Resistor Wednesday: 4/09/03 Quiz; Complementary GatesProblem set #8: Half-Set - out Monday 3/17 and due at 2:30 4/02 in box in 240 Cory – input/output impedance, comparatorsProblem set #9: Monday 3/31 and due at 2:30 4/09 in box in 240 Cory –Static Analysis of an Inverter with simplified EE 42 Device ModelsCopyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003EXAMPLE CIRCUIT: INCREASED INPUT RESISTANCERIN vTEST vIN + - + - GmvIN + - vOUT = 0 RO iTEST RE vE Add resistor REAnalysis: apply iTESTand evaluate vTEST00=−−+TESTINmTESTEEEiRGiRvRvTESTININiRv =ETESTINTESTviRv +=KCLEINmINTESTTESTRRGRiv)1( ++=Check for special case for R0 infiniteIntuitive Explanation:REputs RINon a node whose voltage increases in response to current in RIN.The output has been assumed to be shortedSimilar to the homeworkCopyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003OP-AMP USE AS COMPARATOR (A/D) MODESimple comparator with threshold at 1V. Design lower rail at 0V and upper rail at 2V (logic “1”). A = large (e.g. 102to105 )NOTE: The actual diagram of a comparator would not show an amplifier with “offset” power supply as above. It would be a simple triangle, perhaps with the threshold level (here 1V) specified.If VIN> 1.010 V,V0= 2V = Logic “1”If VIN< 0.99 V,V0= 0V = Logic “0”V0VIN12012+−V0VIN+−1VV0VINComparatorCopyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003Logic Gates – How are they built in practice?What goes in this box?How does it affect digital performance?Pull up NetworkVSUPPLYGroundArray of ValvesVINSignalsA,B,CVOUTA Valve is a TransistorValves in Parallel => NORValves in Series => NANDABCurrent flows when VINis highCan be modeled by a 10kΩ resistorVINABCIN= 100 fFFan OutCopyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003Digital Logic from State-Dependent Three-Terminal DevicesThree-terminal devices such as MOS transistors have characteristics (such as IOUTvs. VOUTcurves) on the output side that can be programmed by changing signals on the input side (such as the input voltage).The input can thus be viewed as changing or programming the ‘State’ of the output of the device.Three-terminal devices whose ‘State’ can be programmed can be used to make digital logic devices for computers that respond to input signals.2Copyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003State-Dependent Three-Terminal Device ElementVOUTInput for ControlSignal to set the StateIOUTOutputVINCopyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003State-Dependent Device IOUTvs. VOUTVOUT(V)035VIN= 0 & 1IOUT(µA)2060100VIN = 3VIN= 5Depending on the state IOUTvs. VOUTis constrained to be on one of these curves by the three-terminal device.Only four states or input values are shown but typically there is a continuum of states.Copyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003Terminology for a Logic CircuitVDDVINVOUTIOUTOutputRPULL UPVDD= Power supply voltage (D is from Drain)IOUT= Current for the device under study.Pull-Down(NMOS)Pull-Down Network = Set of devices used to carry current from the output node to ground to discharge the output node to ground.Pull-Up Network = Set of devices used to carry current from the power supply to the output node to charge the output node to the power supply voltage.VTD= Threshold Voltage value of VINat which the Pull-Down (NMOS transistor) begins to conduct.VOUT-SAT-D= Value of VOUTbeyond which the current IOUT-Dsaturates at the (drain) current saturation value IOUT-SAT-D.Copyright 2001, Regents of University of CaliforniaLecture 16: 03/31/03 A.R. NeureutherVersion Date 03/30/03EECS 42 Intro. electronics for CS Spring 2003Thevenin Model For Pull-Up DeviceVTHEVENIN= VDDIOUT SHORT CIRCUIT= (VDD/RPULL UP)VOUTIOUTOutputVDDRPULL UPExample:VDD= 5V and RPULL UP= 100kΩVTHEVENIN= 5VIOUT SHORT CIRCUIT= 50


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Berkeley ELENG 42 - Lecture Notes

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