) The equation above contains really only three variables in it: Id, Vd, and T. All the other terms are constants. Since in most cases we assume temperature is fairly constant as well, we are really only dealing with two variables: diode current and diode voltage. Based on this realization, re-write the equation as proportionality rather than equality, showing how the two variables of diode current and voltage relate ii) Based on this simplified equation, what would an I vs V graph for a PN junction look like? How does this graph compare against the I vs V graph for a resistor? iii) When "P" and "N" type semiconductor pieces are brought into close contact, free electrons from the "N" piece will rush over to fill holes in the "P" piece, creating a zone on both sides of the contact region devoid of charge carriers. What is this zone called, and what are its electrical characteristics? iv) What happens to the thickness of the region in a PN junction (answer above) when an external voltage is applied to it? v) What effect will this change in this layer thickness, mentioned above, have on overall conductivity through the PN junction? Under what conditions will the conductivity be greatest, and under what conditions will the conductivity be least?

Introductory Circuit Analysis (13th Edition)

13th Edition

ISBN:9780133923605

Author:Robert L. Boylestad

Publisher:Robert L. Boylestad

Chapter1: Introduction

Section: Chapter Questions

Problem 1P: Visit your local library (at school or home) and describe the extent to which it provides literature...

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i) The equation above contains really only three variables in it: Id, Vd, and T. All the other terms are constants. Since in most cases we assume temperature is fairly constant as well, we are really only dealing with two variables: diode current and diode voltage. Based on this realization, re-write the equation as proportionality rather than equality, showing how the two variables of diode current and voltage relate

ii) Based on this simplified equation, what would an I vs V graph for a PN junction look like? How does this graph compare against the I vs V graph for a resistor?

iii) When "P" and "N" type semiconductor pieces are brought into close contact, free electrons from the "N" piece will rush over to fill holes in the "P" piece, creating a zone on both sides of the contact region devoid of charge carriers. What is this zone called, and what are its electrical characteristics?

iv) What happens to the thickness of the region in a PN junction (answer above) when an external voltage is applied to it?

v) What effect will this change in this layer thickness, mentioned above, have on overall conductivity through the PN junction? Under what conditions will the conductivity be greatest, and under what conditions will the conductivity be least?

Aim: The purpose of this experiment is to measure the voltage-current characteristics of a diode.
Background:
At room temperature, an n-type semiconductor (e.g. germanium doped with arsenic) has electrons
available for conduction whose energies lie in the conduction band. Conversely in a p-type
semiconductor (e.g. germanium doped with gallium), conduction is by "holes" (vacancies due to
missing electrons) in the valence band. When two such semi-conductors are joined to form a p-n
junction, electrons will diffuse from the n to the p side and holes from the p to n side provided they
have enough energy to overcome the potential "hill".
The relationship between voltage and current for a PN junction is described by the "diode equation",
or "Shockley's diode equation":
Is (elwer) — 1)
ID = Is e
where,
ID = Current through the PN junction, in amps
Is = PN junction saturation current, in amps (typically 1 picoamp)
e = Euler's number = 2.718281828
q = Electron unit charge, 1.6 x10-19 coulombs
VD = Voltage across the PN junction, in volts
N = Nonideality coefficient, or emission coefficient (typically between 1 and 2)
k = Boltzmann's constant, 1.38 x10-23
T = Junction temperature in Kelvin

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