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Zener Diodes
23 questions By Tony R. Kuphaldt
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Question 22 of 23
∫f(x) dx Calculus alert!
How is the parameter of zener impedance defined for a zener diode? Should an ideal zener diode have a zener impedance figure equal to zero, or infinite? Why?Reveal answer$$Z_{zener} = \frac{\Delta E_{diode}}{\Delta I _{diode}} \ \ \ \ \ \ \ \ \ or \ \ \ \ \ \ \ \ \ Z_{zener} = \frac{dE_{diode}}{dI _{diode}}$$
(The “d” is a calculus symbol, representing a change of infinitesimal magnitude.)
Ideally, a zener diode will have a zener impedance of zero ohms.
Notes:Ask your students to relate a diode’s zener impedance to the slope of its characteristic curve.
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Question 23 of 23
Find one or two real zener diodes and bring them with you to class for discussion. Identify as much information as you can about your diodes prior to discussion:
- Polarity (which terminal is cathode and which is anode)
- Forward voltage drop
- Continuous current rating
- Surge current rating
- Continuous power rating
- Zener voltage rating
Reveal answerIf possible, find a manufacturer’s datasheet for your components (or at least a datasheet for a similar component) to discuss with your classmates. Be prepared to prove the forward voltage drop of your diodes in class, by using a multimeter!
Notes:The purpose of this question is to get students to kinesthetically interact with the subject matter. It may seem silly to have students engage in a “show and tell” exercise, but I have found that activities such as this greatly help some students. For those learners who are kinesthetic in nature, it is a great help to actually touch real components while they’re learning about their function. Of course, this question also provides an excellent opportunity for them to practice interpreting component markings, use a multimeter, access datasheets, etc.
