kristin ackerson, virginia tech ee spring 2002

Kristin Ackerson, Virginia Tech EEKristin Ackerson, Virginia Tech EESpring 2002Spring 2002

Table of ContentsTable of Contents


What are diodes made out of?____________________slide 3What are diodes made out of?____________________slide 3

N-type material_________________________________slide 4N-type material_________________________________slide 4

P-type material_________________________________slide 5P-type material_________________________________slide 5

The pn junction_________________________________slides 6-7The pn junction_________________________________slides 6-7

The biased pn junction___________________________slides 8-9The biased pn junction___________________________slides 8-9

Properties of diodes_____________________________slides 10-11Properties of diodes_____________________________slides 10-11

Diode Circuit Models ____________________________slides 12-16Diode Circuit Models ____________________________slides 12-16

The Q Point____________________________________slides 17-18The Q Point____________________________________slides 17-18

Dynamic Resistance_____________________________slides 19-20Dynamic Resistance_____________________________slides 19-20

Types of diodes and their uses ___________________ slides 21-24Types of diodes and their uses ___________________ slides 21-24

Sources_______________________________________slide 25Sources_______________________________________slide 25

What Are Diodes Made Out Of?What Are Diodes Made Out Of?


• Silicon (Si) and Germanium (Ge) are the two most Silicon (Si) and Germanium (Ge) are the two most common single elements that are used to make Diodes. common single elements that are used to make Diodes. A compound that is commonly used is Gallium A compound that is commonly used is Gallium Arsenide (GaAs), especially in the case of LEDs Arsenide (GaAs), especially in the case of LEDs because of it’s large bandgap. because of it’s large bandgap.

• Silicon and Germanium are both group 4 elements, Silicon and Germanium are both group 4 elements, meaning they have 4 valence electrons. Their meaning they have 4 valence electrons. Their structure allows them to grow in a shape called the structure allows them to grow in a shape called the diamond lattice.diamond lattice.

• Gallium is a group 3 element while Arsenide is a group Gallium is a group 3 element while Arsenide is a group 5 element. When put together as a compound, GaAs 5 element. When put together as a compound, GaAs creates a zincblend lattice structure.creates a zincblend lattice structure.

• In both the diamond lattice and zincblend lattice, each In both the diamond lattice and zincblend lattice, each atom shares its valence electrons with its four closest atom shares its valence electrons with its four closest neighbors. This sharing of electrons is what ultimately neighbors. This sharing of electrons is what ultimately allows diodes to be build. When dopants from groups allows diodes to be build. When dopants from groups 3 or 5 (in most cases) are added to Si, Ge or GaAs it 3 or 5 (in most cases) are added to Si, Ge or GaAs it changes the properties of the material so we are able to changes the properties of the material so we are able to make the P- and N-type materials that become the make the P- and N-type materials that become the diode.diode.

SiSi+4+4

SiSi+4+4

SiSi+4+4

Si Si +4+4

SiSi+4+4

SiSi+4+4

SiSi+4+4

SiSi+4+4

SiSi+4+4

The diagram above shows the The diagram above shows the 2D structure of the Si crystal. 2D structure of the Si crystal.

The light green lines The light green lines represent the electronic represent the electronic bonds made when the bonds made when the

valence electrons are shared. valence electrons are shared. Each Si atom shares one Each Si atom shares one

electron with each of its four electron with each of its four closest neighbors so that its closest neighbors so that its

valence band will have a full 8 valence band will have a full 8 electrons.electrons.

N-Type MaterialN-Type Material


N-Type Material:N-Type Material: When extra valence electrons are introduced When extra valence electrons are introduced into a material such as silicon an n-type into a material such as silicon an n-type material is produced. The extra valence material is produced. The extra valence electrons are introduced by putting electrons are introduced by putting impurities or dopants into the silicon. The impurities or dopants into the silicon. The dopants used to create an n-type material dopants used to create an n-type material are Group V elements. The most commonly are Group V elements. The most commonly used dopants from Group V are arsenic, used dopants from Group V are arsenic, antimony and phosphorus. antimony and phosphorus.

The 2D diagram to the left shows the extra The 2D diagram to the left shows the extra electron that will be present when a Group V electron that will be present when a Group V dopant is introduced to a material such as dopant is introduced to a material such as silicon. This extra electron is very mobile. silicon. This extra electron is very mobile.

+4+4+4+4

+5+5

+4+4

+4+4+4+4+4+4

+4+4+4+4

P-Type MaterialP-Type Material


P-Type Material:P-Type Material: P-type material is produced when the dopant P-type material is produced when the dopant that is introduced is from Group III. Group that is introduced is from Group III. Group III elements have only 3 valence electrons III elements have only 3 valence electrons and therefore there is an electron missing. and therefore there is an electron missing. This creates a hole (h+), or a positive charge This creates a hole (h+), or a positive charge that can move around in the material. that can move around in the material. Commonly used Group III dopants are Commonly used Group III dopants are aluminum, boron, and gallium.aluminum, boron, and gallium.

The 2D diagram to the left shows the hole The 2D diagram to the left shows the hole that will be present when a Group III dopant that will be present when a Group III dopant is introduced to a material such as silicon. is introduced to a material such as silicon. This hole is quite mobile in the same way the This hole is quite mobile in the same way the extra electron is mobile in a n-type material. extra electron is mobile in a n-type material.

+4+4+4+4

+3+3

+4+4

+4+4+4+4+4+4

+4+4+4+4

The PN JunctionThe PN Junction


Steady StateSteady State11

PP nn

- - - - - -- - - - - -

- - - - - -- - - - - -

- - - - - -- - - - - -

- - - - - -- - - - - -

- - - - - -- - - - - -

+ + + + + + + + + + ++

+ + + + + + + + + + ++

+ + + + + + + + + + ++

+ + + + + + + + + + ++

+ + + + + + + + + + ++

NaNa NdNdMetallurgical Metallurgical

JunctionJunction

Space Charge Space Charge RegionRegionionized ionized

acceptorsacceptorsionized ionized donorsdonors

E-FieldE-Field

++++__ __

h+ drifth+ drift h+ diffusionh+ diffusion e- diffusione- diffusion e- drifte- drift== ==

The PN JunctionThe PN JunctionSteady StateSteady State


PP nn

- - - - - - - - - -

- - - - - - - - - -

- - - - - - - - - -

- - - - - - - - - -

+ + + + ++ + + + +

+ + + + ++ + + + +

+ + + + + + + + + +

+ + + + ++ + + + +

NaNa NdNdMetallurgical Metallurgical

JunctionJunction

Space Charge Space Charge RegionRegionionized ionized

acceptorsacceptorsionized ionized donorsdonors

E-FieldE-Field

++++__ __

h+ drifth+ drift h+ diffusionh+ diffusion e- diffusione- diffusion e- drifte- drift== ==== ==

When no external source When no external source is connected to the pn is connected to the pn junction, diffusion and junction, diffusion and

drift balance each other drift balance each other out for both the holes out for both the holes

and electronsand electrons

Space Charge Region:Space Charge Region: Also called the depletion region. This region Also called the depletion region. This region includes the net positively and negatively charged regions. The space includes the net positively and negatively charged regions. The space charge region does not have any free carriers. The width of the space charge charge region does not have any free carriers. The width of the space charge region is denoted by W in pn junction formula’s.region is denoted by W in pn junction formula’s.

Metallurgical Junction:Metallurgical Junction: The interface where the p- and n-type materials meet.The interface where the p- and n-type materials meet.

Na & Nd:Na & Nd: Represent the amount of negative and positive doping in number of Represent the amount of negative and positive doping in number of carriers per centimeter cubed. Usually in the range of 10carriers per centimeter cubed. Usually in the range of 101515 to 10 to 102020..

The Biased PN JunctionThe Biased PN Junction


PP nn

++__

Applied Applied Electric FieldElectric Field

Metal Metal ContactContact

““Ohmic Ohmic Contact”Contact”

(Rs~0)(Rs~0)

++__

VVappliedapplied

II

The pn junction is considered biased when an external voltage is applied. The pn junction is considered biased when an external voltage is applied. There are two types of biasing: Forward bias and Reverse bias. There are two types of biasing: Forward bias and Reverse bias.

These are described on then next slide.These are described on then next slide.

The Biased PN JunctionThe Biased PN Junction


Forward Bias:Forward Bias: In forward bias the depletion region shrinks slightly in In forward bias the depletion region shrinks slightly in width. With this shrinking the energy required for width. With this shrinking the energy required for charge carriers to cross the depletion region decreases charge carriers to cross the depletion region decreases exponentially. Therefore, as the applied voltage exponentially. Therefore, as the applied voltage increases, current starts to flow across the junction. increases, current starts to flow across the junction. The barrier potential of the diode is the voltage at The barrier potential of the diode is the voltage at which appreciable current starts to flow through the which appreciable current starts to flow through the diode. The barrier potential varies for different diode. The barrier potential varies for different materials.materials.

Reverse Bias:Reverse Bias: Under reverse bias the depletion region widens. This Under reverse bias the depletion region widens. This causes the electric field produced by the ions to cancel causes the electric field produced by the ions to cancel out the applied reverse bias voltage. A small leakage out the applied reverse bias voltage. A small leakage current, Is (saturation current) flows under reverse bias current, Is (saturation current) flows under reverse bias conditions. This saturation current is made up of conditions. This saturation current is made up of electron-hole pairs being produced in the depletion electron-hole pairs being produced in the depletion region. Saturation current is sometimes referred to as region. Saturation current is sometimes referred to as scale current because of it’s relationship to junction scale current because of it’s relationship to junction temperature.temperature.

VVappliedapplied > 0 > 0

VVappliedapplied < 0 < 0

Properties of DiodesProperties of Diodes


Figure 1.10 – The Diode Transconductance CurveFigure 1.10 – The Diode Transconductance Curve22

• VVDD = Bias Voltage = Bias Voltage

• IIDD = Current through = Current through Diode. IDiode. IDD is Negative is Negative for Reverse Bias and for Reverse Bias and Positive for Forward Positive for Forward BiasBias

• IISS = Saturation = Saturation CurrentCurrent

• VVBRBR = Breakdown = Breakdown VoltageVoltage

• VV = Barrier Potential = Barrier Potential

VoltageVoltage

VVDD

IIDD (mA)(mA)

(nA)(nA)

VVBRBR

~V~V

IISS

Properties of DiodesProperties of DiodesThe Shockley EquationThe Shockley Equation


• The transconductance curve on the previous slide is characterized by The transconductance curve on the previous slide is characterized by the following equation:the following equation:

IIDD = I = ISS(e(eVVDD//VVTT – 1) – 1)• As described in the last slide, IAs described in the last slide, IDD is the current through the diode, I is the current through the diode, ISS is is

the saturation current and Vthe saturation current and VDD is the applied biasing voltage. is the applied biasing voltage.

• VVTT is the thermal equivalent voltage and is approximately 26 mV at room is the thermal equivalent voltage and is approximately 26 mV at room temperature. The equation to find Vtemperature. The equation to find VTT at various temperatures is: at various temperatures is:

VVTT = = kTkT qq

k = 1.38 x 10k = 1.38 x 10-23-23 J/K T = temperature in Kelvin q = 1.6 x 10 J/K T = temperature in Kelvin q = 1.6 x 10-19-19 C C

is the emission coefficient for the diode. It is determined by the way is the emission coefficient for the diode. It is determined by the way the diode is constructed. It somewhat varies with diode current. For a the diode is constructed. It somewhat varies with diode current. For a silicon diode silicon diode is around 2 for low currents and goes down to about 1 at is around 2 for low currents and goes down to about 1 at higher currentshigher currents

Properties of DiodesProperties of Diodes

MathCAD Example - ApplicationMathCAD Example - Application

Diode Circuit ModelsDiode Circuit Models


The Ideal Diode The Ideal Diode ModelModel

The diode is designed to allow current to flow in The diode is designed to allow current to flow in only one direction. The perfect diode would be a only one direction. The perfect diode would be a perfect conductor in one direction (forward bias) perfect conductor in one direction (forward bias) and a perfect insulator in the other direction and a perfect insulator in the other direction (reverse bias). In many situations, using the ideal (reverse bias). In many situations, using the ideal diode approximation is acceptable.diode approximation is acceptable.

Example: Assume the diode in the circuit below is ideal. Determine the Example: Assume the diode in the circuit below is ideal. Determine the value of Ivalue of IDD if a) V if a) VAA = 5 volts (forward bias) and b) V = 5 volts (forward bias) and b) VAA = -5 volts (reverse = -5 volts (reverse

bias)bias)

++

__VVAA

IIDD

RRS S = 50 = 50 a) With Va) With VAA > 0 the diode is in forward bias > 0 the diode is in forward bias

and is acting like a perfect conductor so:and is acting like a perfect conductor so:

IIDD = V = VAA/R/RSS = 5 V / 50 = 5 V / 50 = 100 mA = 100 mA

b) With Vb) With VAA < 0 the diode is in reverse bias < 0 the diode is in reverse bias

and is acting like a perfect insulator, and is acting like a perfect insulator, therefore no current can flow and Itherefore no current can flow and IDD = 0. = 0.



The Ideal Diode with The Ideal Diode with Barrier PotentialBarrier Potential

This model is more accurate than the simple This model is more accurate than the simple ideal diode model because it includes the ideal diode model because it includes the approximate barrier potential voltage. approximate barrier potential voltage. Remember the barrier potential voltage is the Remember the barrier potential voltage is the voltage at which appreciable current starts to voltage at which appreciable current starts to flow.flow.

Example: To be more accurate than just using the ideal diode model Example: To be more accurate than just using the ideal diode model include the barrier potential. Assume Vinclude the barrier potential. Assume V = 0.3 volts (typical for a = 0.3 volts (typical for a

germanium diode) Determine the value of Igermanium diode) Determine the value of IDD if V if VAA = 5 volts (forward bias). = 5 volts (forward bias).

++

__VVAA

IIDD

RRS S = 50 = 50 With VWith VA A > 0 the diode is in forward bias > 0 the diode is in forward bias and is acting like a perfect conductor and is acting like a perfect conductor so write a KVL equation to find Iso write a KVL equation to find IDD::

0 = V0 = VAA – I – IDDRRSS - V - V

IIDD = V = VAA - V - V = 4.7 V = 94 mA = 4.7 V = 94 mA

RRSS 50 50

VV

++

VV++


The Ideal Diode The Ideal Diode with Barrier with Barrier

Potential and Potential and Linear Forward Linear Forward

Resistance Resistance

This model is the most accurate of the three. It includes a This model is the most accurate of the three. It includes a linear forward resistance that is calculated from the slope of linear forward resistance that is calculated from the slope of the linear portion of the transconductance curve. However, the linear portion of the transconductance curve. However, this is usually not necessary since the Rthis is usually not necessary since the RFF (forward (forward resistance) value is pretty constant. For low-power resistance) value is pretty constant. For low-power germanium and silicon diodes the Rgermanium and silicon diodes the RFF value is usually in the value is usually in the 2 to 5 ohms range, while higher power diodes have a R2 to 5 ohms range, while higher power diodes have a RFF value closer to 1 ohm.value closer to 1 ohm.

Linear Portion of Linear Portion of transconductance transconductance

curvecurve

VVDD

IIDD

VVDD

IIDDRRFF = = VVDD

IIDD


++VV RRFF


The Ideal Diode The Ideal Diode with Barrier with Barrier

Potential and Potential and Linear Forward Linear Forward

Resistance Resistance


Example: Assume the diode is a low-power diode Example: Assume the diode is a low-power diode with a forward resistance value of 5 ohms. The with a forward resistance value of 5 ohms. The barrier potential voltage is still: Vbarrier potential voltage is still: V = 0.3 volts (typical = 0.3 volts (typical

for a germanium diode) Determine the value of Ifor a germanium diode) Determine the value of IDD if if

VVAA = 5 volts. = 5 volts.

++

__VVAA

IIDD

RRS S = 50 = 50

VV++

RRFF

Once again, write a KVL equation Once again, write a KVL equation for the circuit:for the circuit:

0 = V0 = VAA – I – IDDRRSS - - VV - I - IDDRRFF

IIDD = V = VAA - V - V = 5 – 0.3 = 85.5 mA = 5 – 0.3 = 85.5 mA

RRSS + R + RFF 50 + 5 50 + 5



Values of ID for the Three Different Diode Circuit ModelsValues of ID for the Three Different Diode Circuit Models

Ideal Diode Model

Ideal Diode Model with

Barrier Potential Voltage

Ideal Diode Model with

Barrier Potential and

Linear Forward Resistance

ID 100 mA 94 mA 85.5 mA

These are the values found in the examples on previous These are the values found in the examples on previous slides where the applied voltage was 5 volts, the barrier slides where the applied voltage was 5 volts, the barrier potential was 0.3 volts and the linear forward resistance potential was 0.3 volts and the linear forward resistance

value was assumed to be 5 ohms.value was assumed to be 5 ohms.

The Q PointThe Q Point


The operating point or Q point of the diode is the quiescent or no-The operating point or Q point of the diode is the quiescent or no-signal condition. The Q point is obtained graphically and is really only signal condition. The Q point is obtained graphically and is really only

needed when the applied voltage is very close to the diode’s barrier needed when the applied voltage is very close to the diode’s barrier potential voltage. The example potential voltage. The example 33 below that is continued on the next below that is continued on the next

slide, shows how the Q point is determined using the slide, shows how the Q point is determined using the transconductance curve and the load line.transconductance curve and the load line.

++

__VVAA

= 6V= 6V

IIDD

RRS S = 1000 = 1000

VV++

First the load line is found by substituting in First the load line is found by substituting in different values of Vdifferent values of V into the equation for I into the equation for IDD using using

the ideal diode with barrier potential model for the the ideal diode with barrier potential model for the diode. With Rdiode. With RSS at 1000 ohms the value of R at 1000 ohms the value of RFF

wouldn’t have much impact on the results.wouldn’t have much impact on the results.

IIDD = V = VAA – V – V

RRSS

Using V Using V values of 0 volts and 1.4 volts we obtain values of 0 volts and 1.4 volts we obtain

IIDD values of 6 mA and 4.6 mA respectively. Next values of 6 mA and 4.6 mA respectively. Next

we will draw the line connecting these two points we will draw the line connecting these two points on the graph with the transconductance curve. on the graph with the transconductance curve.

This line is the load line.This line is the load line.

The Q PointThe Q Point

IIDD (mA)(mA)

VVDD (Volts)(Volts)

22

44

66

88

1010

1212

0.20.2 0.40.4 0.60.6 0.80.8 1.01.0 1.21.2 1.41.4

The The transconductance transconductance

curve below is for a curve below is for a Silicon diode. The Silicon diode. The

Q point in this Q point in this example is located example is located at 0.7 V and 5.3 mA.at 0.7 V and 5.3 mA.

4.64.6


0.70.7

5.35.3

Q Point: Q Point: The intersection of the The intersection of the load line and the load line and the transconductance curve.transconductance curve.

Capacitance and Voltage of PN Capacitance and Voltage of PN JunctionsJunctions

Diode Operation – Animation

Webpage LinkWebpage Link

http://jas2.eng.buffalo.edu/applets/education/pn/cv/index.html

Dynamic ResistanceDynamic Resistance


The dynamic resistance of the diode is mathematically determined The dynamic resistance of the diode is mathematically determined as the inverse of the slope of the transconductance curve. as the inverse of the slope of the transconductance curve.

Therefore, the equation for dynamic resistance is:Therefore, the equation for dynamic resistance is:

rrFF = = VVTT

IIDD

The dynamic resistance is used in determining the voltage drop The dynamic resistance is used in determining the voltage drop across the diode in the situation where a voltage source is across the diode in the situation where a voltage source is

supplying a sinusoidal signal with a dc offset.supplying a sinusoidal signal with a dc offset.

The ac component of the diode voltage is found using the The ac component of the diode voltage is found using the following equation:following equation:

vvFF = v = vac ac r rFF

rrFF + R + RSS

The voltage drop through the diode is a combination of the ac and The voltage drop through the diode is a combination of the ac and dc components and is equal to:dc components and is equal to:

VVDD = V = V + v + vFF

Dynamic ResistanceDynamic Resistance


Example:Example: Use the same circuit used for the Q point example but Use the same circuit used for the Q point example but change the voltage source so it is an ac source with a dc offset. The change the voltage source so it is an ac source with a dc offset. The source voltage is now, vsource voltage is now, vinin = 6 + sin(wt) Volts. It is a silicon diode so the = 6 + sin(wt) Volts. It is a silicon diode so the

barrier potential voltage is still 0.7 volts.barrier potential voltage is still 0.7 volts.

++

vvinin

IIDD

RRS S = 1000 = 1000

VV++

The DC component of the circuit is the The DC component of the circuit is the same as the previous example and same as the previous example and therefore Itherefore IDD = = 6V – 0.7 V6V – 0.7 V = 5.2 mA = 5.2 mA

1000 1000 rrFF = = VVT T = = 1 * 26 mV1 * 26 mV = 4.9 = 4.9

IID D 5.3 mA5.3 mA

= 1 is a good approximation if the dc = 1 is a good approximation if the dc current is greater than 1 mA as it is in this current is greater than 1 mA as it is in this

example.example.vvFF = v = vacac r rFF = sin(wt) V 4.9 = sin(wt) V 4.9 = 4.88 sin(wt) mV = 4.88 sin(wt) mV

rrFF + R + RSS 4.9 4.9 + 1000 + 1000

Therefore, VTherefore, VDD = 700 + 4.9 sin (wt) mV (the voltage drop across the = 700 + 4.9 sin (wt) mV (the voltage drop across the

diode) diode)


Types of Diodes and Their UsesTypes of Diodes and Their Uses

PN Junction PN Junction Diodes:Diodes:

Are used to allow current to flow in one direction Are used to allow current to flow in one direction while blocking current flow in the opposite while blocking current flow in the opposite direction. The pn junction diode is the typical diode direction. The pn junction diode is the typical diode that has been used in the previous circuits.that has been used in the previous circuits.

AA KK

Schematic Symbol for a PN Schematic Symbol for a PN Junction DiodeJunction Diode

PP nn

Representative Structure for Representative Structure for a PN Junction Diodea PN Junction Diode

Zener Diodes:Zener Diodes: Are specifically designed to operate under reverse Are specifically designed to operate under reverse breakdown conditions. These diodes have a very breakdown conditions. These diodes have a very accurate and specific reverse breakdown voltage.accurate and specific reverse breakdown voltage.

AA KK

Schematic Symbol for a Schematic Symbol for a Zener DiodeZener Diode



Schottky Schottky Diodes:Diodes:

These diodes are designed to have a very fast These diodes are designed to have a very fast switching time which makes them a great diode for switching time which makes them a great diode for digital circuit applications. They are very common digital circuit applications. They are very common in computers because of their ability to be switched in computers because of their ability to be switched on and off so quickly. on and off so quickly. AA KK

Schematic Symbol for a Schematic Symbol for a Schottky DiodeSchottky Diode

Shockley Shockley Diodes:Diodes:

The Shockley diode is a four-layer diode while other The Shockley diode is a four-layer diode while other diodes are normally made with only two layers. diodes are normally made with only two layers. These types of diodes are generally used to control These types of diodes are generally used to control the average power delivered to a load. the average power delivered to a load.

AA KK

Schematic Symbol for a Schematic Symbol for a four-layer Shockley Diodefour-layer Shockley Diode



Light-Emitting Light-Emitting Diodes:Diodes:

Light-emitting diodes are designed with a very large Light-emitting diodes are designed with a very large bandgap so movement of carriers across their bandgap so movement of carriers across their depletion region emits photons of light energy. depletion region emits photons of light energy. Lower bandgap LEDs (Light-Emitting Diodes) emit Lower bandgap LEDs (Light-Emitting Diodes) emit infrared radiation, while LEDs with higher bandgap infrared radiation, while LEDs with higher bandgap energy emit visible light. Many stop lights are now energy emit visible light. Many stop lights are now starting to use LEDs because they are extremely starting to use LEDs because they are extremely bright and last longer than regular bulbs for a bright and last longer than regular bulbs for a relatively low cost. relatively low cost.

AA KK

Schematic Symbol for a Schematic Symbol for a Light-Emitting DiodeLight-Emitting Diode

The arrows in the LED The arrows in the LED representation indicate representation indicate

emitted light.emitted light.



Photodiodes:Photodiodes: While LEDs emit light, Photodiodes are sensitive to While LEDs emit light, Photodiodes are sensitive to received light. They are constructed so their pn received light. They are constructed so their pn junction can be exposed to the outside through a junction can be exposed to the outside through a clear window or lens.clear window or lens.

In Photoconductive mode the saturation current In Photoconductive mode the saturation current increases in proportion to the intensity of the increases in proportion to the intensity of the received light. This type of diode is used in CD received light. This type of diode is used in CD players.players.

In Photovoltaic mode, when the pn junction is In Photovoltaic mode, when the pn junction is exposed to a certain wavelength of light, the diode exposed to a certain wavelength of light, the diode generates voltage and can be used as an energy generates voltage and can be used as an energy source. This type of diode is used in the source. This type of diode is used in the production of solar power.production of solar power.

AA KK

AA KK

Schematic Symbols for Schematic Symbols for PhotodiodesPhotodiodes

SourcesSourcesDailey, Denton. Dailey, Denton. Electronic Devices and Circuits, Discrete and Integrated.Electronic Devices and Circuits, Discrete and Integrated. Prentice Hall, New Prentice Hall, New

Jersey: 2001. (pp 2-37, 752-753)Jersey: 2001. (pp 2-37, 752-753)2 2 Figure 1.10. The diode transconductance curve, pg. 7Figure 1.10. The diode transconductance curve, pg. 7

Figure 1.15. Determination of the average forward resistance of a diode, pg 11Figure 1.15. Determination of the average forward resistance of a diode, pg 11

33 Example from pages 13-14 Example from pages 13-14

Liou, J.J. and Yuan, J.S. Semiconductor Device Physics and Simulation. Plenum Press, Liou, J.J. and Yuan, J.S. Semiconductor Device Physics and Simulation. Plenum Press, New York: 1998.New York: 1998.

Neamen, Donald. Neamen, Donald. Semiconductor Physics & Devices. Basic Principles.Semiconductor Physics & Devices. Basic Principles. McGraw-Hill, McGraw-Hill, Boston: 1997. (pp 1-15, 211-234)Boston: 1997. (pp 1-15, 211-234)

11 Figure 6.2. The space charge region, the electric field, and the forces acting on Figure 6.2. The space charge region, the electric field, and the forces acting on the charged carriers, pg 213. the charged carriers, pg 213.


kristin ackerson, virginia tech ee spring 2002

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