63.2 Junction Diodes and its Characteristicsi(mA)Thediode i-vrelationship(Notethescaleexpansion)compression)ForwardCompressedVzKscale0.7VOU0.5Vcut-in voltageeooeReverseBreakdown+UNC(nA)2025/11/27
2025/11/27 6 (mA) (nA) The diode i–v relationship (Note the scale expansion / compression) cut-in voltage 3.2 Junction Diodes and its Characteristics
3.3The Diode ModelsMathematic Model :nVr -1)/=nVForwardbiasedReverse biasedwhereI.saturationcurrentkTthermal voltage(~25 mv at room temperature)VT :qn = 1~2 (In general, n = 1)2025/11/27
2025/11/27 7 ⚫ Mathematic Model： − = − s n V v s n V v s I I e i I e T T ( 1) Forward biased Reverse biased 3.3 The Diode Models where 𝑰𝒔 saturation current 𝒗𝑻 = 𝒌𝑻 𝒒 thermal voltage(~25 mv at room temperature) 𝒏 = 𝟏𝟐 (In general, n = 1)
83.3TemperaturedependenceTT22mVPT>TVoltagedrop@-2mV/oCTemperaturedependenceofthediodeforwardcharacteristic2025/11/27
2025/11/27 8 Temperature dependence of the diode forward characteristic Voltage drop @-2 mV/C 3.3 Temperature dependence
93.3The Diode ModelsCircuit Model : usually derived byapproximating the curve into piecewise-lineAccording to practical applications,there aredifferentmodels,suchas>Simplifieddiode model>Theconstant-voltage-dropmodelSmall-signalmodel>High-frequency modelZenerDiode Model2025/11/27
2025/11/27 9 ⚫ Circuit Model : usually derived by approximating the curve into piecewise-line ⚫ According to practical applications, there are different models, such as ➢ Simplified diode model ➢ The constant-voltage-drop model ➢ Small-signal model ➢ High-frequency model ➢ Zener Diode Model 3.3 The Diode Models
103.3ldeal Diode Model·Forwardbiasshortcircuit·Reversebias→opencircuit-ReversebiasForwardbias02025/11/27
2025/11/27 10 3.3 Ideal Diode Model ⚫ Forward bias → short circuit ⚫ Reverse bias → open circuit