Zener diode

[OrangeArav]

I'm having trouble understanding how to find the slopes in this circuit:

Problem statement: The PWL model for the Zener diode in the circuit above is shown below. The source is a triangle wave, as shown below. Sketch the voltage across the Zener diode. Indicate voltage levels of both the source and the Zener diode when the slope changes.
(i) Forward bias: Vd0 = 0.55V, rd = 15 ohm
(ii) Breakdown: Vz0 = 4.8V, rz = 6 ohm


My work is shown below:

 

[Harald Kapp]

The slope is given by the parameters of the PWL statement. The longer the time between two points of the PWL statement, the flater the slope; the shorter teh time, the steeper the slope.
The rest follows from the simulation.

 

[OrangeArav]

Harald Kapp,

It's just a simple ?
If that's the case then the slope seems a bit too high... For instance, the first section is 572.92


and the 2nd is 19814.8,

 

[Harald Kapp]

It's just a simple ?

Yes it is.

In your circuit the slope of the voltage source's signal has only a negligible effect on the simulation result (due to the capacitance of the zener diode which forms a low passs with the resistor, but the capacitance is very small).

If that's the case then the slope seems a bit too high...

Why should this be too high? The absolute value of the slope is not of interest. The problem statement is:

Indicate voltage levels of both the source and the Zener diode when the slope changes.

, so all you have to do is look at the points where the slope changes and write down the voltage levels of source and zener diode at these points.

 

[OrangeArav]

Ok, understood. Thank you!