Above is a circuit where: D1 is a 10V(breakdown) zener diode, V1 is a voltage source which varies from 11V to 5OV DC and R1 is a 1k resistor. My aim is to identify the dynamic/bulk resistance of the zener diode by using LTspice.
I simulated the circuit such that 0 - 40mA current passes through the zener. The resulting V-I plot can be seen above.
Lets call Vz is the zener voltage and Iz is the zener current. What I uderstand from what I read is that, the dynamic/bulk resistance of the zener diode refers to the derivative dVz/dIz when Vz is above the knee voltage.
My questions are:
1-) Can I use this plot to obtain Vz/Iz which correcponds to the dynamic resistance? If so, is there a standard at which current the derivative corresponds to the bulk resistance?
2-) How can I plot the derivative of this plot i.e dVz/dIz in LTspice?
Edit: DC Sweep:
When I did a DC sweep, results at 5mA (since data sheet takes 5mA as reference):
dVz/dIz (total dynamic impedance I guess) is 25 Ohm from the above plot. But the data sheet says at 5mA max zener impedance is 20 Ohm.
And the voltage at 5mA Iz is 10.2V in the plot. But the data sheet says nominal voltage at 5mA is 10V.
Is there anything wrong with the way I compare?