A light-emitting diode has a forward drop of at its rated current

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

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

Problem

A light-emitting diode has a forward drop of

2.0\,\mathrm{V}

at its rated current. It is to be run from a

6.0\,\mathrm{V}

ideal supply at a target current of

15\,\mathrm{mA}

, with a series resistor carrying the current-limiting job. ((a)) Calculate the series resistor needed and state the nearest E12 preferred value (

1, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2

times a power of ten). ((b)) Using that preferred value, calculate the actual current in the LED.

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