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Diode models

Conducts primarily in one direction Compare its models in the same order shown in the component inspector.

Symbol

Diode symbol
Default symbol for a new Diode component.

Model choice belongs to each placed Diode component. Changing one component does not change other instances or the default for future placements.

1

Practical

Continuous forward I/V with junction capacitance. No reverse recovery or breakdown.

Default
Qualified analyses
  • Operating point
  • DC sweep
  • AC sweep
  • Transient

Model definition

The Practical model fits a continuous diode curve through the entered forward-voltage and forward-current point. Series resistance controls the additional drop at higher current.

A constant junction capacitance carries displacement current during voltage transitions.

Equations

Vj=VD−IDRS,IS=IFexp⁡ ⁣(VF−IFRSηVT)−1V_j=V_D-I_D R_S,\qquad I_S=\frac{I_F}{\exp\!\left(\frac{V_F-I_F R_S}{\eta V_T}\right)-1}
The entered forward point (Vꜰ, Iꜰ) determines saturation current after removing the series-resistance drop.
ID=IS ⁣[exp⁡ ⁣(VjηVT)−1]+CJdVjdtI_D=I_S\!\left[\exp\!\left(\frac{V_j}{\eta V_T}\right)-1\right]+C_J\frac{\mathrm dV_j}{\mathrm dt}
Terminal current is the continuous junction current plus constant-capacitance displacement current.
η=1.8,VT=25.852 mV at 27∘C,τT=0\eta=1.8,\qquad V_T=25.852\,\mathrm{mV}\ \text{at}\ 27^\circ\mathrm C,\qquad \tau_T=0
Emission coefficient and calibration temperature are fixed. Zero transit time removes stored diffusion charge.

Parameters

ParameterDefaultAccepted values
Forward voltageForward voltage at the stated forward current.0.7 V at 10 mAGreater than 0; reference condition greater than 0
Series resistanceBulk series resistance of the forward path.100 mΩGreater than 0
Junction capacitanceConstant junction capacitance.10 pFGreater than 0

Limits

  • Reverse recovery and avalanche breakdown are omitted.
  • Junction capacitance is constant rather than voltage dependent.
  • Temperature, noise, and device-to-device spread are omitted.
2

Power

Fast charge-free rectifier with a calibrated forward drop and resistance.

Qualified analyses
  • Operating point
  • DC sweep
  • Transient

Model definition

The Power model is a charge-free, piecewise-linear rectifier for converter simulation.

Its conducting branch uses the entered forward point and series resistance to set a voltage knee and on-state slope.

Equations

VK=VF−IFRSV_K=V_F-I_F R_S
The stated forward-voltage point sets the zero-current intercept after the series-resistance drop is removed.
VD≈VK+IDRSwhen conductingV_D\approx V_K+I_D R_S\quad\text{when conducting}
Above the knee, series resistance sets the forward-voltage slope.

Parameters

ParameterDefaultAccepted values
Forward voltageForward voltage at the stated forward current.0.8 V at 1 AGreater than 0; reference condition greater than 0
Series resistanceOn-state slope resistance above the calibrated forward-voltage knee.50 mΩGreater than 0

Limits

  • Junction capacitance, stored charge, reverse recovery, leakage, breakdown, and temperature are omitted.
  • Use the Recovery model or a qualified vendor model for commutation edges and switching-loss estimates.
  • AC analysis is not qualified for this piecewise-linear system model.
3

Recovery

Datasheet-calibrated forward path, leakage, capacitance, and reverse-recovery charge.

Qualified analyses
  • Operating point
  • DC sweep
  • AC sweep
  • Transient

Model definition

Recovery keeps the Practical forward path and adds a leakage branch plus stored charge in the junction.

You can enter either reverse-recovery charge at a prior forward current or reverse-recovery time. OhmSpice maps the selected datum to one charge-storage time constant.

Equations

Vj=VD−IDRS,IS=IFexp⁡ ⁣(VF−IFRS1.8VT)−1V_j=V_D-I_D R_S,\qquad I_S=\frac{I_F}{\exp\!\left(\frac{V_F-I_F R_S}{1.8V_T}\right)-1}
The forward junction and its saturation current use the same calibration as the Practical model.
τT=QrrIForτT=trr\tau_T=\frac{Q_{rr}}{I_F}\quad\text{or}\quad\tau_T=t_{rr}
The selected recovery datum sets the effective transit time.
Rleak=VRIR−ISR_{\mathrm{leak}}=\frac{V_R}{I_R-I_S}
The parallel leakage resistor supplies the requested reverse current after subtracting the junction's saturation current.
ID=Ij+VDRleak+CJdVjdt,Qdiff≈τTIjI_D=I_j+\frac{V_D}{R_{\mathrm{leak}}}+C_J\frac{\mathrm dV_j}{\mathrm dt},\qquad Q_{\mathrm{diff}}\approx\tau_T I_j
The total model combines junction, leakage, capacitance, and first-order stored diffusion charge.

Parameters

ParameterDefaultAccepted values
Forward voltageForward voltage at the stated forward current.0.8 V at 1 AGreater than 0; reference condition greater than 0
Series resistanceBulk series resistance of the forward path.50 mΩGreater than 0
Junction capacitanceEffective reverse-biased junction capacitance.100 pFGreater than 0
Reverse leakageReverse leakage current at the stated reverse voltage.10 µA; at VR 100 VGreater than 0; reference condition greater than 0
Recovery dataUse whichever reverse-recovery datum the datasheet provides.Qrr at IFQrr at IF, trr
Reverse-recovery chargeStored reverse-recovery charge at the stated prior forward current.Shown when Recovery data is Qrr at IF.100 nC; at IF 1 AGreater than 0; reference condition greater than 0
Reverse-recovery timeEffective stored-charge lifetime derived from the datasheet trr.Shown when Recovery data is trr.100 nsGreater than 0

Limits

  • The model predicts stored charge, not recovery softness or a complete current waveform.
  • Recovery does not vary with temperature, di/dt, or operating history beyond the entered reference point.
  • Avalanche breakdown and nonlinear capacitance are omitted.
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