of R6, respectively. Both 2N4401 and MPSA06 transistors
can support peak currents up to 500 mA and are usable
in this circuit.
It would also be easy to use a larger enclosure for the
tester and include a digital panel meter that would read
out the zener diode voltage without requiring a separate
meter, or two to read voltage and current simultaneously.
There you have it! I hope this circuit measures up for
you as much as it has for me! NV
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References
Switchmode Power Supply Handbook, Keith Billings,
McGraw-Hill, 1989, pp. 2. 49 to 2. 62.
VERSA-PAC Transformer Information:
www.digikey.com/product-search/
en?mpart=VPH2-1600-R&vendor=283
EDN Magazine, June 10, 2010, Design Ideas, pp. 51-52,
“Circuit lets you measure zener voltages and test LEDs.”
EDN Magazine, November 25, 2004, pp. 104-106,
“Zener test circuit serves as a DC source.”
November 2014 31
