# SPICE Diode

SPICE-compatible diode

**Libraries:**

Simscape /
Electrical /
Additional Components /
SPICE Semiconductors

## Description

The SPICE Diode block represents a SPICE-compatible diode.

SPICE, or Simulation Program with Integrated Circuit Emphasis,
is a simulation tool for electronic circuits. You can convert some SPICE subcircuits into
equivalent Simscape™
Electrical™ models using the Environment Parameters block and
SPICE-compatible blocks from the Additional Components library. For more
information, see `subcircuit2ssc`

.

### Equations

Variables for the SPICE Diode block equations include:

Variables that you define by specifying parameters for the SPICE Diode block. The visibility of some of the parameters depends on the value that you set for other parameters. For more information, see Parameters.

Geometry-adjusted variables, which depend on several values that you specify using parameters for the SPICE Diode block. For more information, see Geometry-Adjusted Variables.

Temperature,

*T*, which is`300.15`

`K`

by default. You can use a different value by specifying parameters for the SPICE Diode block or by specifying parameters for both the SPICE Diode block and an Environment Parameters block. For more information, see Diode Temperature.Temperature-dependent variables. For more information, see Temperature Dependence.

Minimal conductance,

*GMIN*, which is`1e–12`

`1/Ohm`

by default. You can use a different value by specifying a parameter for an Environment Parameters block. For more information, see Minimal Conduction.Thermal voltage,

*V*. For more information, see Thermal Voltage._{t}

**Geometry-Adjusted Variables**

Several variables in the equations for the SPICE diode model consider the geometry of the device that the block represents. These geometry-adjusted variables depend on variables that you define by specifying SPICE Diode block parameters. The geometry-adjusted variables depend on these variables:

*AREA*— Area of the device*SCALE*— Number of parallel connected devicesThe associated unadjusted variable

The table includes the geometry-adjusted variables and the defining equations.

Variable | Description | Equation |
---|---|---|

CJO_{d} | Geometry-adjusted zero-bias junction capacitance |
$$CJ{O}_{d}=CJO*AREA*SCALE$$ |

IBV_{d} | Geometry-adjusted reverse breakdown current |
$$IB{V}_{d}=IBV*AREA*SCALE$$ |

IS_{d} | Geometry-adjusted saturation current |
$$I{S}_{d}=IS*AREA*SCALE$$ |

RS_{d} | Geometry-adjusted series resistance |
$$R{S}_{d}=\frac{RS}{AREA*SCALE}$$ |

**Diode Temperature**

You can use these options to define diode temperature, *T*:

Fixed temperature — The block uses a temperature that is independent from the circuit temperature when the

**Model temperature dependence using**parameter in the**Temperature**settings of the Spice Diode block is set to`Fixed temperature`

. For this model, the block sets*T*equal to*TFIXED*.Device temperature — The block uses a temperature that depends on circuit temperature when the

**Model temperature dependence using**parameter in the**Temperature**settings of the Spice Diode block is set to`Device temperature`

. For this model, the block defines temperature as$$T={T}_{C}+TOFFSET$$

Where:

*T*is the circuit temperature._{C}If there is no Environment Parameters block in the circuit,

*T*is equal to 300.15 K._{C}If there is an Environment Parameters block in the circuit,

*T*is equal to the value that you specify for the_{C}**Temperature**parameter in the**Spice**settings of the Environment Parameters block. The default value for the**Temperature**parameter is`300.15`

`K`

.*TOFFSET*is the offset local circuit temperature.

**Minimal Conduction**

Minimal conductance, *GMIN*, has a default value of
`1e–12`

`1/Ohm`

. To specify a different value:

If there is not an Environment Parameters block in the diode circuit, add one.

In the

**Spice**settings of the Environment Parameters block, specify the desired*GMIN*value for the**GMIN**parameter.

**Thermal Voltage**

Thermal voltage, *V _{t}*, is defined by
the equation

$${V}_{t}=N\frac{k*T}{q}$$

Where:

*N*is the emission coefficient.*T*is the diode temperature. For more information, see Diode Temperature.*k*is the Boltzmann constant.*q*is the elementary charge on an electron.

**Current-Voltage Equations**

These equations define the relationship between the diode current,
*I _{d}*, and the diode voltage,

*V*. As applicable, the model parameters are first adjusted for temperature. For more information, see Temperature Dependence.

_{d}$${I}_{d}=AREA*({I}_{fwd}-{I}_{rev})$$

$${I}_{fwd}={I}_{nrm}*{K}_{inj}+{I}_{rec}*{K}_{gen}$$

$${I}_{rev}={I}_{revh}+{I}_{revl}$$

$${I}_{nrm}={I}_{S}{e}^{{V}_{d}/(N*Vt)-1}$$

$${I}_{rec}={I}_{SR}{e}^{{V}_{d}/(NR*Vt)-1}$$

$${K}_{inj}={\left(\frac{IKF}{IKF+{I}_{nrm}}\right)}^{0.5}$$

$${K}_{gen}={\left[{\left(\frac{1-{V}_{d}}{VJ}\right)}^{2}+0.005\right]}^{\frac{M}{2}}$$

$${I}_{revh}=IBV*{e}^{-\frac{{V}_{d}+BV}{NBV*Vt}}$$

$${I}_{revl}=IBVL*{e}^{-\frac{{V}_{d}+BV}{NBVL*Vt}}$$

Where:

*I*is the forward current._{fwd}*I*is the reverse current._{rev}*I*is the normal current._{nrm}*I*is the recombination current._{rec}*K*is the high-injection factor._{inj}*K*is the generation factor._{gen}*I*is the high-level breakdown current._{revh}*I*is the low-level breakdown current._{revl}*V*is thermal voltage. For more information, see Thermal Voltage._{t}*I*is the saturation current._{S}*I*is the recombination current._{SR}*IKF*is the forward knee current.*VJ*is the junction potential.*N*is the emission coefficient.*NR*is the reverse emission coefficient.*NBV*is the reverse breakdown emission coefficient.*NBVL*is the low-level reverse breakdown ideality factor.*M*is the grading coefficient.*BV*is the reverse breakdown voltage.*IBV*is the reverse breakdown current.*IBVL*is the low-level reverse breakdown knee current.

**Junction Charge Model**

The table shows the equations that define the relationship between the diode charge
*Q _{d}*, and the diode voltage,

*V*. As applicable, the model parameters are first adjusted for temperature. For more information, see Temperature Dependence.

_{d}

V
Range_{d} | Q
Equation_{d} |
---|---|

$${V}_{d}<FC*VJ$$ | $${Q}_{d}=TT*AREA*{I}_{fwd}+CJ{O}_{d}*VJ*\frac{1-{\left(1-\frac{{V}_{d}}{VJ}\right)}^{1-M}}{1-M}$$ |

$${V}_{d}\ge FC*VJ$$ | $$\begin{array}{l}{Q}_{d}=TT*AREA*{I}_{fwd}+\\ \text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}CJ{O}_{d}*\left(F1+\frac{F3*\left({V}_{d}-FC*VJ\right)+\left(\frac{M}{2*VJ}\right)*\left({V}_{d}^{2}-{\left(FC*VJ\right)}^{2}\right)}{F2}\right)\text{}\end{array}$$ |

Where:

*FC*is the forward bias depletion capacitance coefficient.*VJ*is the junction potential.*TT*is the transit time.*CJO*is the geometry-adjusted zero-bias junction capacitance. For more information, see Geometry-Adjusted Variables._{d}*M*is the grading coefficient.$$F1=VJ*(1-{(1-FC)}^{(1-M)})/(1-M)$$

$$F2={(1-FC)}^{(1+M)}$$

$$F3=1-FC*(1+M)$$

**Temperature Dependence**

The relationship between the geometry-adjusted saturation current and the diode temperature is

$$I{S}_{d}(T)=I{S}_{d}*{\left(T/TMEAS\right)}^{\frac{XTI}{N}}*{e}^{\left(\frac{T}{TMEAS}-1\right)*\frac{EG}{N*{V}_{t}}}$$

Where:

*IS*is the geometry-adjusted saturation current. For more information, see Geometry-Adjusted Variables._{d}*T*is the diode temperature. For more information, see Diode Temperature.*TMEAS*is the parameter extraction temperature.*XTI*is the saturation current temperature exponent.*N*is the emission coefficient.*EG*is the activation energy.*V*is thermal voltage. For more information, see Thermal Voltage._{t}

The relationship between the recombination current and the diode temperature is

$$ISR(T)=ISR*{\left(\frac{T}{TMEAS}\right)}^{\frac{XTI}{NR}}*{e}^{\left(\frac{T}{TMEAS}-1\right)*\frac{EG}{NR*{V}_{t}}}$$

Where:

*ISR*is the recombination current.*NR*is the reverse emission coefficient.

The relationship between the forward knee current and the diode temperature is

$$IKF(T)=IKF*\left[1+TIKF*(T-TMEAS)\right]$$

Where:

*IKF*is the forward knee current.*TIKF*is the linear IKF temperature coefficient.

The relationship between the breakdown voltage and the diode temperature is

$$BV(T)=BV*\left[1+TBV1*(T-TMEAS)+TBV2*{(T-TMEAS)}^{2}\right]$$

Where:

*BV*is the breakdown voltage.*TBV1*is the linear BV temperature coefficient.*TBV2*is the quadratic BV temperature coefficient.

The relationship between the ohmic resistance and the diode temperature is

$$RS(T)=RS*\left[1+TRS1*(T-TMEAS)+TRS2*{(T-TMEAS)}^{2}\right]$$

Where:

*RS*is the ohmic resistance.*TRS1*is the linear RS temperature coefficient.*TRS2*is the quadratic RS temperature coefficient.

The relationship between the junction potential and the diode temperature is

$$VJ(T)=VJ*\left(\frac{T}{TMEAS}\right)-3*Vt*\mathrm{ln}\left(\frac{T}{TMEAS}\right)-\left(\frac{T}{TMEAS}\right)*E{G}_{TMEAS}+E{G}_{T}$$

Where:

*VJ*is the junction potential.*EG*is the activation energy for the temperature at which the diode parameters were measured. The defining equation is $$E{G}_{TMEAS}=1.16eV-\left(7.02e-4*TMEA{S}^{2}\right)/\left(TMEAS+1108\right)$$._{TMEAS}*EG*is the activation energy for the diode temperature. The defining equation is $$E{G}_{T}=1.16eV-\left(7.02e-4*{T}^{2}\right)/\left(T+1108\right)$$._{T}

The relationship between the geometry-adjusted diode zero-bias junction capacitance and the diode temperature is

$$CJ{O}_{d}(T)=CJ{O}_{d}*\left[1+M*\left(400e-6*\left(T-TMEAS\right)-\frac{VJ(T)-VJ}{VJ}\right)\right]$$

Where:

*CJO*is the geometry-adjusted zero-bias junction capacitance. For more information, see Geometry-Adjusted Variables._{d}*M*is the grading coefficient.

## Assumptions and Limitations

The block does not support noise analysis.

The block applies initial conditions across junction capacitors and not across the block ports.

## Ports

### Conserving

## Parameters

## Extended Capabilities

## Version History

**Introduced in R2008a**