Pspice: derivative function in probe

[ram0001]

Hi Guys,
I am stuck at a point and needs help.
The thing is I am doing MOSFET inverters using Pspice.
I am getting its VTC (voltage characteristic Curve) But I don't know how to get derivative of this curve in order to obtain some parameters required for Noise margin.
Here is the file:

.model NMOD NMOS (LEVEL=1, VTO=0.6 GAMMA=0 LAMBDA=0 KP=60U)
.model PMOD PMOS (LEVEL=1, VTO=-0.8 GAMMA=0 LAMBDA=0 KP=20U)

***********
* CIRCUIT *
***********

VDD 3 0 DC 3
VGS 1 0 DC 3
M1 2 1 0 0 NMOD L=0.8U W=2U
M2 2 1 3 3 PMOD L=0.8U W=10U
.OP
.DC LIN VGS 0 3 0.1
.PLOT DC V(2)
.PROBE
.END

I have 9.1 Student ,Demo version. I referred to user manual... and it says I used use probe function 'd()' to get derivative but that's not working. It says invalid expressions.
I am taking 'd()' at 'V(2)'.
I would really appreciate if some one can help me out.
Thanks,

 

[ram0001]

I got it.
thanks

 

[ravenprp]

Hi there,

Thank you for reaching out for help with your Pspice project. It sounds like you are trying to obtain the derivative of your VTC curve in order to calculate the noise margin for your MOSFET inverter.

To get the derivative of a curve in Pspice, you can use the 'd()' function in the Probe window. However, it looks like you may be using it incorrectly. The 'd()' function takes in two arguments - the variable you want to take the derivative of and the variable you want to differentiate with respect to.

In your case, you want to take the derivative of the voltage at node 2 (V(2)) with respect to the gate-source voltage (VGS). Therefore, the correct syntax for the 'd()' function would be 'd(V(2),VGS)'. This should give you the derivative of your VTC curve at each point.

I hope this helps you with your project. If you continue to have trouble, please don't hesitate to reach out for further assistance. Best of luck!