A Zener diode reference is specified with a slope (differential) resistance at its rated

PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Semiconductor devices and analogue circuits · Semiconductor devices and analogue circuits

Electronics for Measurement, Ch The junction: an element whose current is exponential in its voltage

Problem

A 6.2 V6.2\,\mathrm{V} Zener diode reference is specified with a slope (differential) resistance rz=50 Ωr_z=50\,\Omega at its rated 10 mA10\,\mathrm{mA}. A change of load draws the Zener's own current down from 10 mA10\,\mathrm{mA} to 5.0 mA5.0\,\mathrm{mA}. Treat rzr_z as constant over this change. ((a)) One way to estimate the movement of the Zener voltage is to treat 6.2 V/10 mA=620 Ω6.2\,\mathrm{V}/10\,\mathrm{mA}=620\,\Omega as “the Zener's resistance” and multiply by the 5.0 mA5.0\,\mathrm{mA} change. Carry this out and comment on the result. ((b)) Give the correct change in the Zener voltage, and state which resistance the data sheet's rzr_z actually describes.

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