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