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Finding 1st and 2nd derivative of current and voltage at t=0+.
##### Question
Is it possible to find out di/dt and (d^2) i / (dt)^2 at some time instants . for ex. in network analysis there are problems for finding out current and voltage at t=0+ and also the 1st and 2nd derivative of current and voltage at t=0+.

Oscad Schematic-Creation-and-Simulation None min None sec 18-06-14, 2:19 p.m. ashish123

There is no direct function to find derivatives at a particular node in Oscad. However, you can create a differentiator using opamp and then use it to find derivatives.
18-06-14, 3:04 p.m. shambhu
One quick solution that I could think of is to type the following in the Ngspice terminal:

plot deriv(v(node#)) - where node# is the node whose voltage derivative you need to plot

for derivative of current, you might have to first place a current plot in the schematic, then on simulation you will get a plot of i(v_u#). Now you can type plot deriv(i(v_u#)) on the Ngspice terminal to get the derivative of this current.
18-06-14, 11:57 p.m. rakhiwarriar

One quick solution that I could think of is to type the following in the Ngspice terminal:

plot deriv(v(node#)) - where node# is the node whose voltage derivative you need to plot

for derivative of current, you might have to first place a current plot in the schematic, then on simulation you will get a plot of i(v_u#). Now you can type plot deriv(i(v_u#)) on the Ngspice terminal to get the derivative of this current.
18-06-14, 11:57 p.m. rakhiwarriar