115.1Practical Source ConnectionREa二EcRREB2025/11/27
2025/11/27 11 5.1 Practical Source Connection
125.1Current Flow in the TransistorReverse-biasedForward-biased动画1CollestedDEsgnjectedCEEronseutronelectronsECLEInjected holes (iB)Recombinedelectrons(iB2)1O'CROW'REBoEVBE+VCRCurrent flow in an npn transistor biased to operate in theactive mode.2025/11/27
2025/11/27 12 Current flow in an npn transistor biased to operate in the active mode. 5.1 Current Flow in the Transistor 动画
135.2Current EquationTerminal currentrelationshipit=ib +ic22025/11/27
5.2 Current Equation 2025/11/27 13 ⚫ Terminal current relationship c b e iE iC iB iE= iB + iC
145.2 Collector CurrentCollectorcurrentisthedriftcurrent.Themagnitude of collector current is almostindependentofvoltageacrossCBjunctionThis current can be calculated by thegradientoftheprofileofelectronconcentrationinbaseregionwhere Iis the saturation current,also calledcurrentscalefactor2025/11/27
5.2 Collector Current T BE V v C n s i I = I e 2025/11/27 14 ⚫ Collector current is the drift current. The magnitude of collector current is almost independent of voltage across CB junction. ⚫ This current can be calculated by the gradient of the profile of electron concentration in base region where Is is the saturation current, also called current scale factor
155.2Saturation Current·Expressionfor saturationcurrent:AqD.n;WN.WEBJCBJEmitterBaseCollector(n)depletion(p)depletion(n)regionregionThe saturationcurrentisastrong function withElectronconcentrationtemperature due to intrinsicnp (ideal)carrierconcentrationHolen,(0)concentrationIts valueis usuallyintherange of 10-12A to 10-18A个Distance (x)Pn (O)n,(withPnorecombination)EffectivebasewidthW2025/11/27
5.2 Saturation Current ⚫ Expression for saturation current: 2025/11/27 15 N W A qD n W A qD n I A E n p E n i s 2 0 = = ⚫ The saturation current is a strong function with temperature due to intrinsic carrier concentration. ⚫ Its value is usually in the range of 10-12A to 10-18A