A raw supply of direct voltage carries peak-to-peak ripple

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 raw supply of

12\,\mathrm{V}

direct voltage carries

1.0\,\mathrm{V}

peak-to-peak ripple. It feeds a

1.4\,\mathrm{k}\Omega

series resistor into a

5.1\,\mathrm{V}

Zener diode (data sheet:

r_z=40\,\Omega

at the operating current), with the load drawing a current small enough to leave the resistor and Zener carrying essentially the same current. Someone argues: “the Zener holds its voltage exactly at

5.1\,\mathrm{V}

whatever happens upstream, so the output has no ripple at all.” ((a)) Is that reasoning correct? If not, say what it leaves out. ((b)) Calculate the actual peak-to-peak ripple appearing on the Zener's output.

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