Diode (exponential)

Shockley diode with saturation current and thermal voltage.

  • electrical
  • Modelica Standard Library
  • 2 ports
  • 3 parameters
BlockDiode (exponential)KinddiodeShockleyLibrarySemiconductors

Description

A diode with the exponential Shockley characteristic plus a parallel leakage resistance. Use it where the forward voltage or the soft turn-on matters.

Above 15 · Vt the exponential continues as a straight line with the same slope, which keeps the solver stable at large currents.

Example

Diodes and a Zener regulator Three diode models rectifying a 10 V sine, and a Zener diode holding 5.1 V.

10 V 50 Hz ADiodeLoad Av AGround A10 V 50 Hz BIdeal diodeLoad Bv BGround B10 V 50 Hz CDiode (exponential)Load Cv CGround C12 VR 100 ΩZener 5.1 Vv ZenerGround (Zener)
In Gradara, select a Diode (exponential) block and press F1, then choose Open example. It opens as a new model in My models, ready to run.

Also in this example:DC voltageVoltage sensorGroundResistorDiodeAC voltageIdeal diodeZener diode

Ports

Conserving terminals 2

  • +pelectrical

    Anode. Current into p is counted as positive (forward).

  • −nelectrical

    Cathode.

Parameters

  • Saturation currentIds0.000001 A

    ≥ 0

    Saturation current, in amperes. Positive; a larger value lowers the forward voltage.

  • Thermal voltageVt0.04 V

    ≥ 0

    Voltage equivalent of temperature (n · k · T / q), in volts. Positive; it sets how sharp the knee is.

  • Parallel resistanceR100000000 Ω

    ≥ 0

    Parallel leakage resistance, in ohms. Positive; the default 100 MΩ is negligible in most circuits.

Equations

Modelica
v = p.v − n.v, i = p.i
i = Ids · (exp(v / Vt) − 1) + v / R, for v ≤ 15 · Vt
i = Ids · (exp(15) · (1 + v / Vt − 15) − 1) + v / R, for v > 15 · Vt

Implementation

Modelica Standard Library 4.1.0Modelica.Electrical.Analog.Semiconductors.Diode
MSL documentation

Assumptions and limitations

  • No temperature dependence (Vt is fixed), reverse breakdown, junction capacitance, or reverse recovery.
  • No series resistance; above 15 · Vt the linear continuation acts as one.

Tips

  • With the defaults, the forward voltage is about 0.28 V at 1 mA and 0.55 V at 1 A.

See also

Select a block in Gradara and press F1 to open its page offline.