1. ECE 255: Fall 2019 Purdue University
ECE 255: Zener Diodes (Sedra and Smith, 4.4) Mark Lundstrom School of ECE Purdue University West Lafayette, IN USA
Lundstrom: Fall 2019

2. Goal for this lecture
Analyze circuits like this.
Lundstrom: Fall 2019

3. Outline Zener diodes and applications Zener diode model
Zener model parameters
Zener diode circuits
Lundstrom: Fall 2019

4. Diode IV: reverse breakdown
-Zener (negative temp coeff)
-avalanche (positive temp coeff.)
Lundstrom: Fall 2019

5. Diode IV: reverse breakdown
slope
Zener diode
“knee current”
Lundstrom: Fall 2019

6. Recall: ideal voltage source
Lundstrom: Fall 2019

7. Recall: real voltage source
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8. “battery regulator”
Lundstrom: Fall 2019

9. Zener diodes
need a model here
Lundstrom: Fall 2019

10. Modeling the Zener diode
Model parameters:
Lundstrom: Fall 2019

11. Outline Zener diodes and applications Zener diode model
Zener model parameters
Zener diode circuits
Lundstrom: Fall 2019

12. Finding the model parameters
Lundstrom: Fall 2019

13. Outline Zener diodes and applications Zener diode model
Zener model parameters
Zener diode circuits
Lundstrom: Fall 2019

14. “Zener shunt regulator”
At the nominal input voltage, what is VL when IL = 0?
Lundstrom: Fall 2019

15. At the nominal input voltage, what is VL when IL = 0?
Zener shunt regulator
KVL
At the nominal input voltage, what is VL when IL = 0?

16. “Line regulation”
KVL
What is the change in output voltage for a +/- 1 V change in input voltage?

17. “Load regulation” KVL KVL
What is the change in output voltage if the load draws 2 mA of current?
Lundstrom: Fall 2019

18. “Load regulation” (the easy way)
What is the change in output voltage if the load draws 2 mA of current?
Lundstrom: Fall 2019

19. Maximum load current
What maximum load current can be drawn if the regulator is to operate properly?
Lundstrom: Fall 2019

20. Summary A good Zener diode in breakdown is like a good battery.
The Zener diode model consists of an ideal battery in series with a resistor.
To insure that we are operating in the breakdown region, must be sure that IZ > IZK.
Lundstrom: Fall 2019

21. Zener diodes Zener diodes and applications Zener diode model
Zener model parameters
Zener diode circuits
Lundstrom: Fall 2019