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Wrong JFET parameters when using nested param .DC sweep

MK202608101044

Hello, I didn't find a bug reporting feature, so I will try here.

When simulating a TEMP sweep I stumbled across a bug with njf model. Its parameters get calculated differently based on the chosen sweep type. I created a minimal example here:

Input:

.param vd_p=0

vd d 0 {vd_p}

j1 d 0 0 myjfet

.model myjfet njf t_measured=25

.dc TEMP LIST -50 -25 0 25 50 75 100 125 150 175 200 ; param vd_p 0 1 1

Output:

...
myjfet (T_Current -50 T_Measured 25)
PB 1.064E+00
...
myjfet (T_Current -25 T_Measured 25)
PB 1.044E+00
...
myjfet (T_Current 0 T_Measured 25)
PB 1.022E+00
...
myjfet (T_Current 25 T_Measured 25)
PB 1.000E+00
...
myjfet (T_Current 50 T_Measured 25)
PB 9.767E-01
...
myjfet (T_Current 75 T_Measured 25)
PB 9.526E-01
...
myjfet (T_Current 100 T_Measured 25)
PB 9.277E-01
...
myjfet (T_Current 125 T_Measured 25)
PB 9.019E-01
...
myjfet (T_Current 150 T_Measured 25)
PB 8.755E-01
...
myjfet (T_Current 175 T_Measured 25)
PB 8.484E-01
...
myjfet (T_Current 200 T_Measured 25)
PB 8.206E-01
...
myjfet (T_Current 27 T_Measured 25)
PB 9.982E-01
...

This example produces normal results. However, if I add a nested parameter sweep, the calculated JFET parameters are wrong, resulting even in an error.

Input:

.param vd_p=0

vd d 0 {vd_p}

j1 d 0 0 myjfet

.model myjfet njf t_measured=25

.dc TEMP LIST -50 -25 0 25 50 75 100 125 150 175 200 param vd_p 0 1 1

Output:

...
myjfet (T_Current -50 T_Measured 25)
PB 1.064E+00
...
myjfet (T_Current -25 T_Measured 25)
PB 1.097E+00
...
myjfet (T_Current 0 T_Measured 25)
PB 1.111E+00
...
myjfet (T_Current 25 T_Measured 25)
PB 1.111E+00
...
myjfet (T_Current 50 T_Measured 25)
PB 1.097E+00
...
myjfet (T_Current 75 T_Measured 25)
PB 1.066E+00
...
myjfet (T_Current 100 T_Measured 25)
PB 1.010E+00
...
myjfet (T_Current 125 T_Measured 25)
PB 9.157E-01
...
myjfet (T_Current 150 T_Measured 25)
PB 7.558E-01
...
myjfet (T_Current 175 T_Measured 25)
PB 4.814E-01
...
ERROR(ORPSIM-15007): Model myjfet has negative PB.
...
myjfet (T_Current 200 T_Measured 25)
PB -2.389E-03
...
myjfet (T_Current 27 T_Measured 25)
PB 9.982E-01
...

When using .step instead of the nested sweep, it works normally. It also works normally using nested sweep, when sweeping a source and not a param.

Tested on version PSpice 25.1.0, PSpice 24.1.0 and PSpice 17.4.0

Best regards,

Matej

  • 0

    Hi,

    Could you share the complete simulation output (.OUT file) for both.
      • Working case (TEMP sweep only)
      • Failing case (TEMP sweep + parameter sweep)
    Also, just to confirm the same simulation circuit was used to perform above, right?
  • 0 in reply to IshaS

    Hello, the minimal example I provided is the whole circuit. The problem came up during different simulation, but the problem is the same -> JFET parameters get calculated incorrectly causing the JFET to behave incorrectly as well.

    I had trouble uploading the .out files, so I just copied the contents here. (it worked at first, but then after refresh I was not able to upload them)

    • Working:

    **** 08/12/26 09:21:54 *** PSpice 25.1.0 (14 September 2025) ** ID# 0 ********


    **** CIRCUIT DESCRIPTION


    ******************************************************************************


    .param vd_p=0

    vd d 0 {vd_p}

    j1 d 0 0 myjfet

    .model myjfet njf t_measured=25

    .dc TEMP LIST -50 -25 0 25 50 75 100 125 150 175 200 ; param vd_p 0 1 1


    **** 08/12/26 09:21:54 *** PSpice 25.1.0 (14 September 2025) ** ID# 0 ********


    **** Junction FET MODEL PARAMETERS


    ******************************************************************************


    myjfet
    NJF
    T_Measured 25
    T_Current 27
    VTO -2
    BETA 100.000000E-06


    Model-Specific Temperatures During Sweep Param value = -50

    **** JFET MODEL PARAMETERS

    myjfet (T_Current -50 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 2.071E-21
    PB 1.064E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = -25

    **** JFET MODEL PARAMETERS

    myjfet (T_Current -25 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 9.554E-19
    PB 1.044E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 0

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 0 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.474E-16
    PB 1.022E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 25

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 25 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.000E-14
    PB 1.000E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 50

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 50 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 3.602E-13
    PB 9.767E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 75

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 75 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 7.884E-12
    PB 9.526E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 100

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 100 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.158E-10
    PB 9.277E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 125

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 125 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.229E-09
    PB 9.019E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 150

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 150 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 9.976E-09
    PB 8.755E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 175

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 175 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 6.475E-08
    PB 8.484E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 200

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 200 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 3.480E-07
    PB 8.206E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures After Sweep Param value = 27

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 27 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.361E-14
    PB 9.982E-01
    CGS 0.000E+00
    CGD 0.000E+00

    JOB CONCLUDED

    **** 08/12/26 09:21:54 *** PSpice 25.1.0 (14 September 2025) ** ID# 0 ********


    **** JOB STATISTICS SUMMARY


    ******************************************************************************

    Total job time (using Solver 1) = .02

    • Failing:


    **** 08/12/26 09:19:04 *** PSpice 25.1.0 (14 September 2025) ** ID# 0 ********


    **** CIRCUIT DESCRIPTION


    ******************************************************************************


    .param vd_p=0

    vd d 0 {vd_p}

    j1 d 0 0 myjfet

    .model myjfet njf t_measured=25

    .dc TEMP LIST -50 -25 0 25 50 75 100 125 150 175 200 param vd_p 0 1 1


    **** 08/12/26 09:19:04 *** PSpice 25.1.0 (14 September 2025) ** ID# 0 ********


    **** Junction FET MODEL PARAMETERS


    ******************************************************************************


    myjfet
    NJF
    T_Measured 25
    T_Current 27
    VTO -2
    BETA 100.000000E-06


    Model-Specific Temperatures During Sweep Param value = 0

    **** JFET MODEL PARAMETERS

    myjfet (T_Current -50 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 2.071E-21
    PB 1.064E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = -25

    **** JFET MODEL PARAMETERS

    myjfet (T_Current -25 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.979E-25
    PB 1.097E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 0

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 0 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 2.917E-27
    PB 1.111E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 25

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 25 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 2.917E-27
    PB 1.111E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 50

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 50 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.051E-25
    PB 1.097E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 75

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 75 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 8.282E-23
    PB 1.066E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 100

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 100 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 9.589E-19
    PB 1.010E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 125

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 125 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.178E-13
    PB 9.157E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 150

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 150 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.176E-07
    PB 7.558E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 175

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 175 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 7.612E-01
    PB 4.814E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 200

    **** JFET MODEL PARAMETERS


    ERROR(ORPSIM-15007): Model myjfet has negative PB.
    myjfet (T_Current 200 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 2.649E+07
    PB -2.389E-03
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 1

    **** JFET MODEL PARAMETERS

    myjfet (T_Current -50 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 2.071E-21
    PB 1.064E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = -25

    **** JFET MODEL PARAMETERS

    myjfet (T_Current -25 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.979E-25
    PB 1.097E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 0

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 0 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 2.917E-27
    PB 1.111E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 25

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 25 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 2.917E-27
    PB 1.111E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 50

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 50 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.051E-25
    PB 1.097E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 75

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 75 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 8.282E-23
    PB 1.066E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 100

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 100 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 9.589E-19
    PB 1.010E+00
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 125

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 125 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.178E-13
    PB 9.157E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 150

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 150 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.176E-07
    PB 7.558E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 175

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 175 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 7.612E-01
    PB 4.814E-01
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures During Sweep Param value = 200

    **** JFET MODEL PARAMETERS


    ERROR(ORPSIM-15007): Model myjfet has negative PB.
    myjfet (T_Current 200 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 2.649E+07
    PB -2.389E-03
    CGS 0.000E+00
    CGD 0.000E+00


    Model-Specific Temperatures After Sweep Param value = 0

    **** JFET MODEL PARAMETERS

    myjfet (T_Current 27 T_Measured 25)

    VTO -2.000E+00
    BETA 1.000E-04
    IS 1.361E-14
    PB 9.982E-01
    CGS 0.000E+00
    CGD 0.000E+00

    JOB CONCLUDED

    **** 08/12/26 09:19:04 *** PSpice 25.1.0 (14 September 2025) ** ID# 0 ********


    **** JOB STATISTICS SUMMARY


    ******************************************************************************

    Total job time (using Solver 1) = .52

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