Changing Device Parameters in PSpice

Device Model: Diode

PSpice

• Simplest diode model in PSpice uses only the ideal diode equation

• More complex diode models in PSpice include:– Parasitic resistances to account for the linear regions– Breakdown voltage with current multipliers to map the

knee between Io and the current at breakdown

– Temperature dependences of various parameters– Parasitic capacitances to account for the frequency

dependence

PSpice

• Device Simulation packages– Capture– Schematics

• The calculations performed will be identical when using the same device models.

• The GUIs are not the same.• There are minor differences in how the programs

interprets some changes that you make to the device models.

PSpice Schematics

Device Parameters*** Power Diode *** Type of Diode

.MODEL D1N4002-X D Part Number

( IS=14.11E-9 Reverse Saturation Current

N=1.984 Ideality Factor

RS=33.89E-3 Forward Series Resistance

IKF=94.81 High-Level Injection Knee Current in Forward Bias

XTI=3 Temperature Dependence of Reverse Saturation Current

EG=1.110 Energy Bandgap of Si

CJO=51.17E-12 Junction Capacitance at Zero Applied Bias

M=.2762 Grading Coefficient Inversely Proportional to Zener Resistance

VJ=.3905 Turn-on Voltage

FC=.5 Coefficient Associated with Forward Bias Capacitance

ISR=100.0E-12 Reverse Saturation Current During Reverse Bias

NR=2 Ideality Factor During Reverse Bias

BV=100.1 Breakdown Voltage

IBV=10 Current at Breakdown Voltage

TT=4.761E-6 ) Transit Time of Carriers Across p-n Juntion

PSpice Capture

Editing Device Model

• The device parameters can be changed, but will only be changes for the file that you are currently working on. – In Schematics, the changes only apply to the specific

part that you had highlighted when you made the changes.

– In Capture, the changes apply to all components in the file that share the same part model.

– To simulate the Ideal Diode Equation, you can delete the other parameters or set them to zero or a very large number, depending on what would be appropriate to remove their effect from the simulation