# Zener diode

Discussion in 'Electronics Homework Help' started by OrangeArav, Jul 19, 2015.

1. ### OrangeArav

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Jul 14, 2015
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:

2. ### Harald KappModeratorModerator

10,598
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Nov 17, 2011
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.

3. ### OrangeArav

38
0
Jul 14, 2015
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,

4. ### Harald KappModeratorModerator

10,598
2,364
Nov 17, 2011
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).

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

38
0
Jul 14, 2015
Ok, understood. Thank you!