NPN Bipolar Junction(BJT) transistorSymbolConstruction and useThis shows the commonemitter mode which is how wewill use the BJT. Concentrateon the BE junction which lookslike a diode. When this isforward biased, a large currentcan flow from C to E.C = CollectorE = EmitterB = BaseHydraulic analogyThe BJT is a current-controlled current amplifier. That is, asmall current into the base results in a large current fromcollector to emitter.PackageTop-down viewLecture 9: Transistorshttp://www.mine-control.com/zack/transistor/transistor.htmlCool hydraulicanalogies. One error the CE current is reallylarger than the base.Note that there arenormally on andnormally off versions. ECEN 1400 Introduction to Analog and Digital ElectronicsIf we give names to the input and outputlevels, we can construct a reduceddescription of the plot called a truth table:1 2low highhighlowInput OutputLow = 0 High = 1High = 1 Low = 0So the output is high if it isNOT the case that the input ishigh. We thus call this aNOT gate or Inverter.Input OutputPull up resistor causesVO to be high if IC is ~0but allows VO to be low ifthe bottom of the resistoris grounded.Switch, eitheropen or shortSimplifiedoperationhttp://jpkc.njau.edu.cn/szdzjs/ywjc2.htmPlot of VO vs. VICurrent limiting resistor ECEN 1400 Introduction to Analog and Digital ElectronicsRobert R. McLeod, University of Colorado 104Transistor/transistor logic(TTL) NAND gateConsider a circuit like the previous one but now w