ECE3254 Lab01 Diodes Notes (2)

8/9/2019 ECE3254 Lab01 Diodes Notes (2)

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ECE 3254Lab 01a

Rectifier Diodes


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You will need: Multimeter with clip leads

ANDY Board and power supply (4) 1N5819 diode

(1) 1N4001 diode

LEDs

1 red, 1 green, 2 yellow

Resistors(1) 3.3k

(4) 150, 180, or 200

(1) 100

(1) 33

(2) 10 Wires for breadboard

LTspice

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Diodes come in many packages

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Ideal Rectifier Diode Operation

may also be called a switching diode if designed for high frequency

use.

operates as a one-way check valve where current flow occurs onlywhen the diode is forward biased.

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Real diodes and the diode equation Conduction in both directions follows an exponential V-I curve.

The diode current I is given by the exponential diode equation

You may never use this equation, but you can find it easily if you do.

All you really have to understand for most applications A rectifier diode has a typical forward voltage of 0.3V to 1.2V

A rectifier diode has a reverse breakdown voltage that is at least the

diodes Peak Reverse Voltage rating from the spec sheet.

Once diode conduction begins, a very small voltage increase across

the diode will dramatically increase the diode current. You must use

external components to limit a diodes current to a safe value.

The conduction current increases with temperature.

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Exponential conduction

occurs in both directions

Conduction voltage depends

on the diode construction.

You have to watch the ratings

when you build circuits withdiodes.

If the diode is pushed too hard,

other components will be

damaged if the diode fails.

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Rectifier Diode RatingsA real diode has a forward voltage drop and some reverse conduction.

Some important rectifier diode ratings include:

IF(AV)Average Rectified Forward Current

VRRMPeak Repetitive Reverse Voltage

(may also be called PIV or PRV for Peak Inverse/Reverse Voltage)

VFForward Voltage drop

IRReverse Current

PDPower Dissipation

trr reverse recovery time CTtotal junction Capacitance

Exceeding a rating may cause failure!


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Reading the Data Sheet

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Reading the Data Sheet

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1N40011N4007


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Using Rectifier Diodes

Rectifier diodes are normally only operated in

forward condition cutoff

forward voltage below the diodes forward turn-on voltage

reverse voltage below the VRRM/ PRV / PIV rating

The VRRMrating is not an indication of where reverse conduction

actually occurs; it only guarantees that the diode will not break down

before the VRRMrating is reached.

Reverse conduction voltage can not be predicted (see point above).

Because uncontrolled reverse breakdown quickly leads to diode

failure, (which usually damages other circuit components) you

should never attempt to operate a rectifier diode in reverse

conduction.

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Which specs matter, and why? VFis important if voltage drop must be minimized to get maximum

voltage out of a circuit, or to reduce the heat that must be dissipatedby the diode.

IRcan be important if reverse current will be a problem in your circuit

design.

PDis usually OK if you are operating below the maximum current. In

a hot environment, you should make sure that the heat transfer fromthe diode will keep the diode temperature safe.

VRRMcan not be safely exceeded. The ANDY board has a

maximum output of 15V, which can put a maximum of 30V across

a diode if the diode is connected between the two supply rails.Check your spec and determine if this should be a concern.

IF(AV)can not be exceeded for long. The ANDY board can easily

supply over 2A continuously. Check your spec and determine if this

should be a concern.

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What is different about a Schottky diode?

Compared to a regular diode:

The good:

The schottky diode requires a lower forward voltage for conduction

The schottky diode has a considerably shorter switching time.

The bad: The schottky diode has a lower reverse voltage rating

The schottky diode has higher reverse current leakage

The ugly:

Schottky diode reverse leakage increases with temperature This increasing leakage can result in thermal runaway

if the diode is allowed to overheat.

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Identifying the Diode Leads

The diode cathode is identified by a band on the cathode end.

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Light Emitting Diodes (LEDs)

The LED emits light when forward current is

flowing. The light intensity increases with current.

LED useful life is inversely proportional to

current.

Due to their small size, long life, and low power

requirements, LEDs are rapidly replacing other

types of lighting.

The LEDs typical forward voltage is specified

for a current and light intensity.Lower current = lower light levels, but higher

efficiency and longer life.

Reverse voltage ratings are usually low.

Currents increase as temperature increases

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Note: Wikipedia and Google are useful,but try to stay focused!

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Reading LED Specs The Absolute Maximum

Ratings table has the

specs for

max Reverse voltage

max Forward Current

The Electro-Optical

Characteristics table has

specs for

typical Forward Voltage VF

Luminous Intensity IV

Peak Wavelength p

typical Current is found inthe Condition column for

the values of VF, IVand p.

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Using LEDs

Some method of current limiting is required.

The simplest way is to drop unneeded voltage

across a series resistor.

1. Assume the diode voltage will be close to theforward voltage specification given in the

spec sheet.

2. Set the current below the maximum in the

spec sheet.

3. RS = (VSVD) / ID.[from Ohms Law where IRS= VRS/RS]

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Diodes as isolatorsDiodes are useful for connecting multiple devices to one point without

connecting the devices to each other.

An example is the battery isolator, which allows a car alternator to

charge two batteries, but keep the batteries separate from each

other so that both are not discharged when the engine is not

running. Current from the alternator can flow into each battery, but

the diodes block current trying to flow backwards through the

isolator.

The isolator enables you to restart your car (with the 800W

Thumping Bass sound system) after the tailgate party.

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Solar Array Diodes

Shaded solar cells heat if current

is pushed forward through them

Shaded cells draw current if there

is a voltage at the cell terminals.

Solar Panel diodes Diodes bypass shaded cells

Prevents cell heating when other

cells are producing power.

Diodes block reverse current in

shaded cells. Stops battery drain at night.

Eliminates charge bleed in

shaded cell.

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Isolating control functions with diodes

In DC systems, diodes may isolate

switches/controls from each other.

Allows each switch to control some

devices in common, and some

devices separately.

No buttons pressed = both lights off Pressing button A turns bulb 1 on by

providing a ground for bulb 1

Pressing switch B turns both bulbs on

by providing a ground to both bulbs.

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More control functions with diodes No buttons pressed = bulb 4 is on.

Pressing only A or B will leave bulb 4

on with power applied by the other

switch.

Pressing both switch A and switch B will

turn off bulb 4 by removing all power.

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Some automotive applications

Isolators can control

Interior lights

turn/brake lights

fog lights

power windows & locks fuel pumps

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Lab Procedure Tips

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DMM diode measurement

The multimeter has a built-in diode

measurement function, which measures

the probe voltage at a low current.

Place the meter range switch in the

diode/continuity position, connect the

diode to the probe leads, and read the

junction voltage.

The red lead has positive voltage and

acts as the current source. The black

lead is ground.

A current of slightly less than 2mA (with a 2Vmax

limit) is driven through the probe leads, and the

voltage at the probe terminals is measured. This is

a safe way to test diode and transistor junctions.

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Remember from last semester:To measure a current:

you must open the circuit and insert the

meter in series with the circuit.

To reduce the chances of blowing the fuse:

Make sure that the current is safe

before you move the lead to the mA

shunt.

After you have measured a current,

move the red meter lead back to the

VHz jack before making any other

measurement.

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Measuring the diode VI curve

Not required - Curve Given Use the ANDY breadboard +5V

supply.

Use a jumper wire to connect

first one diode, then the other.

Use wires clipped into the meter

leads to probe the voltages.

Because there are many

measurements, its easier (and

safer for your meter fuse) to

measure the voltage across the

resistor and calculate the diode

current using Ohms Law.

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NOTE: For resistance values below 100, first connect the meter for the

measurement, then connect the jumper only briefly.

The resistor(s) will overheat if connected for more than 10 seconds.


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ANDY board pushbuttonsThe two pushbuttons on the ANDY board

are actually logic outputs with limitedcurrent capacity.

On the terminal blocks for each pushbutton

the top four holes are high (+5V) when

the button is released, and low(ground) when the button is pressed.

The bottom four holes are low (ground)

when the button is released, and high

(+5V) when the button is pressed.

Use the top set of holes (+5 when the

button is released) for experiment 01.

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Design and build the switch isolator

Each LED must have a dropping resistor to limit current.

Use diodes to isolate the switch functions

from each other.

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no buttons pressed A pressed B pressed A and B pressed


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Building the diode control isolator Replace each bulb with an LED and series resistor.

Rseries

= V+ - VLED

/ ILED

.

The LEDs are diodes, so not all of the blocking diodes used with the bulbs are

required for the LED circuit to function correctly with 5V applied. You are free to

eliminate the blocking diodes if you wish to simplify the wiring.

Bulb 1 is a Yellow LED and resistor (on when A and/or B is pressed)

Bulb 2 is a Green LED and resistor (on when B is pressed).

Bulb 3 (not shown) is a Red LED which mirrors Bulb 2 (on when A is pressed). Bulb 4 is the second yellow LED (and resistor), which stays lit until both switches

are pressed.

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Completed Diode Isolator Circuit

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LED Polarity

LEDs emit light when current flows in the forward direction.

The flat spot on the LED case flange is the cathode ( - lead).

The anode (+ lead) of an LED is longer (until the leads are cut).

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Wiring tips

Photos are not intended as a wire it this way guide.

Build your circuit one LED at a time, and test for correct operationeach time you add another LED.

Note that you are using the top of the pushbutton function

+5V when the switch is released

0V when the switch is pressed.

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Modeling Diodes with LTspice

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Experimental diode I-V measurement

1N5819 turns on at 0.22V, I 900mA @ 0.50V

1N4001 turns on at 0.62V, I 850mA @ 0.90V

We need to match LTspice simulation to these measured results.

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Test the generic diode modelBuild a swept voltage and diode circuit

Add a voltage source set to 0 Add a ground

Add a generic diode from the toolbar

Add a .op parameter to sweep the

voltage from 0V to 0.9V in 10mVsteps

Connect the wiring

Save the file! Run the simulation

Note the current! This is nota good model for 1N4001 and

1N5819 diodes.

Save this schematic for later

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Change the diode to a 1N5819

Save this file under a new name (i.e. Lab 01

1N5819 or similar).

Right click the diode symbol in the schematic

click Pick New Diode

Select the 1N5819, OK

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Complete the schematic and simulate

To match your experimental results,

set to sweep V1 from 0V to 0.55V.

Save the file

Run the simulation

Measure ID1 [ note I 2.8A at 0.5V ]

A poor matchfor the kit 1N5819!

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Adding 3rdparty models to LTspice

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**************************************

* Model Generated by MODPEX *

*Copyright(c) Symmetry Design Systems*

* All Rights Reserved *

* UNPUBLISHED LICENSED SOFTWARE *

* Contains Proprietary Information *

* Which is The Property of *

* SYMMETRY OR ITS LICENSORS *

*Commercial Use or Resale Restricted *

* by Symmetry License Agreement *

**************************************

* Model generated on Aug 21, 00

* MODEL FORMAT: PSpice

.MODEL D1n5819 d+IS=1.19279e-05 RS=0.0625421 N=1.16517 EG=1.3

+XTI=3.22098 BV=40 IBV=0.001 CJO=1.50114e-10

+VJ=1.5 M=0.590203 FC=0.5 TT=2.6273e-08

+KF=0 AF=1


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Adding 3rdparty models to LTspice

Third-party SPICE models are described as a

.MODEL for intrinsic SPICE devices like diodes and transistors(i.e. 1N4001 diode, 1N5819, diode, 2N3904 transistor)

.SUBCKT defines the component by a collection of circuitry ofintrinsic SPICE devices (i.e. LM 741 OpAmp).

See this video http://www.linear.com/solutions/1083

Google for 1n5819 spice model Schottky Diode models at OnSemi http://www.onsemi.com/pub/Collateral/1N5819.LIB

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WooHoo, first hit!
http://www.linear.com/solutions/1083http://www.onsemi.com/PowerSolutions/supportDoc.do?type=models&rpn=1N4001http://www.onsemi.com/pub/Collateral/1N5819.LIBhttp://www.onsemi.com/pub/Collateral/1N5819.LIBhttp://www.onsemi.com/PowerSolutions/supportDoc.do?type=models&rpn=1N4001http://www.linear.com/solutions/1083


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1N5819 Model text:**************************************










**************************************



.MODEL D1n5819d

+IS=1.19279e-05 RS=0.0625421 N=1.16517 EG=1.3

+XTI=3.22098 BV=40 IBV=0.001 CJO=1.50114e-10

+VJ=1.5 M=0.590203 FC=0.5 TT=2.6273e-08+KF=0 AF=1

From http://www.onsemi.com/pub/Collateral/1N5819.LIB

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Part number is D1n5819, which

you enter for the Value in LTspiceThe separate d designates this part as a diode

Note: you can paste themodel text to the left

directly into your .op

statement in your

schematic.
http://www.onsemi.com/pub/Collateral/1N5819.LIBhttp://www.onsemi.com/pub/Collateral/1N5819.LIB


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Reload the Generic Diode Circuit

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Edit the diode model

Hold Control key and Right click

the diode symbol. Right click on D Value

Set Value to D1n5819

This must match the part

number in the model.

Set the voltage to sweep from 0

to 0.55

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Set .op directive for model parameters

Click .op

You can enter the .lib full-URL-to-the-model

(in this case, the URL is (http://www.onsemi.com/pub/Collateral/1N5819.LIB)

This will copy the model to your local directory. See the video

http://www.linear.com/solutions/1083.

Preferable(most portable for this lab): paste the model statementinto the schematic.

Click.op, set the font size to 1

Paste the model text into

the statement.

The schematic becomes

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http://www.onsemi.com/pub/Collateral/1N5819.LIBhttp://www.linear.com/solutions/1083http://www.linear.com/solutions/1083http://www.onsemi.com/pub/Collateral/1N5819.LIB


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Run the simulation and measure ID1 Save the file under a new name

Run the simulation Measure ID1 [ 2.2A at 0.5V ]

Still does not matchthe kit 1N5819!

But we can edit the model to obtain

0.9A at 0.5V! [ Need I 0.9A at 0.5V ]

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Change the RS series resistance to 0.2Original model from OnSemi

**************************************






* Which is The Property of ** SYMMETRY OR ITS LICENSORS *



**************************************



.MODEL D1n5819 d+IS=1.19279e-05 RS=0.0625421N=1.16517 EG=1.3

+XTI=3.22098 BV=40 IBV=0.001 CJO=1.50114e-10

+VJ=1.5 M=0.590203 FC=0.5 TT=2.6273e-08

+KF=0 AF=1

Change the RS value to 0.2

**************************************






* Which is The Property of ** SYMMETRY OR ITS LICENSORS *



**************************************



.MODEL D1n5819 d

+IS=1.19279e-05 RS=0.2N=1.16517 EG=1.3

+XTI=3.22098 BV=40 IBV=0.001 CJO=1.50114e-10

+VJ=1.5 M=0.590203 FC=0.5 TT=2.6273e-08

+KF=0 AF=1

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Edit the Schematic .op

Right click the model text box on the

schematic Find RS=0.0625421 and change the

value to RS=0.2, hit OK.

Save the file, run the simulation.

This model is close to 0.9A at 0.5V.46


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Upload the schematic to scholar

Add a text box above your schematic with

Your Name, ECE3254 - Lab 01 1N5819

Save the schematic where you can find it.

Answer the questions on the worksheet.

Upload the schematic (.asc) file to

Assignment 01 on scholar.

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The schematic file has a .asc file extension

If your .asc extensions are not visibleand you cant find the schematic

Open windows explorer

Click tools > folder options > view > Uncheck the box for Hide extensions for known file types

Click: Apply > OK

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1N4001 - Reload the Generic Diode Circuit

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Add a 1N4001 model to LTspice See this video http://www.linear.com/solutions/1083

Google for 1N4001 LTspice model After several pages, I found Spice models at OnSemi

See http://www.onsemi.com/pub/Collateral/1N4001RL.LIB

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Google is your friend,

but you have to dig!

1N4001 M d l t t
http://www.linear.com/solutions/1083http://www.onsemi.com/PowerSolutions/supportDoc.do?type=models&rpn=1N4001http://www.onsemi.com/pub/Collateral/1N4001RL.LIBhttp://www.onsemi.com/pub/Collateral/1N4001RL.LIBhttp://www.onsemi.com/PowerSolutions/supportDoc.do?type=models&rpn=1N4001http://www.linear.com/solutions/1083


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1N4001 Model text:**************************************


*Copyright(c) Symmetry Design Systems** All Rights Reserved *





* Modeling services provided by *

* Interface Technologies www.i-t.com ***************************************

.MODEL D1n4001rl d

+IS=1.22478e-08 RS=0.0414786 N=1.83369 EG=0.6

+XTI=0.05 BV=50 IBV=5e-08 CJO=1e-11

+VJ=0.7 M=0.5 FC=0.5 TT=1e-09

+KF=0 AF=1

* Model generated on October 12, 2003

* Model format: PSpice

From http://www.onsemi.com/pub/Collateral/1N4001RL.LIB

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Part number is D1n4001r1, wh ichyou enter for the Value in LTspice

Note: you can paste the

model text to the leftdirectly into your .op

statement in your

schematic.
http://www.onsemi.com/pub/Collateral/1N4001RL.LIBhttp://www.onsemi.com/pub/Collateral/1N4001RL.LIB


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Edit the Generic Diode Model

Hold Control key and Right click

the diode symbol.

Right click on D Value

Set Value to D1n7001rl

This must match the part

number in the model.

Note: the text is D1n7001rl.The last character is the

letter l (not a 1).

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S f


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Set .op directive for model parameters

Click .op

set the font size to 1

Paste the model text into

the statement.

The schematic becomes

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Run the simulationcheck results

The schematic should

similar to the one shownon the right.

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The simulation result is

similar to the curve you

plotted experimentally.

S


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Submit your LTspice schematic to scholar

After you have successfully competed the schematic and simulation

Use a text box to enter Your Name, ECE3254Lab 01 1N4001 onthe LTspice schematic. Save the file where you can find it!

Upload your schematic file to the Lab Worksheet assignment on

scholar.

The schematic is the file with arrowyour filename may be

different, but it will have .asc for the file extension If your .asc extensions are not visibleand you cant find the schematic, open

windows explorer and click tools > folder options > view >

uncheck the box for Hide extensions for known file types > Apply > OK

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LTspice resources

Linear Technology software pagedownload LTspice

LT WikiFAQs, tips, component libraries, tutorials

Ltspice getting started guide(ppt) at CDS Linear

Google search for LTspice circuits will find many useful web sites.

Add a model to LTspice: http://www.linear.com/solutions/1083

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http://www.linear.com/designtools/software/http://ltwiki.org/http://ltwiki.org/http://ltwiki.org/http://cds.linear.com/docs/en/ltspice/LTspiceGettingStartedGuide.pdfhttp://www.linear.com/solutions/1083http://www.linear.com/solutions/1083http://cds.linear.com/docs/en/ltspice/LTspiceGettingStartedGuide.pdfhttp://ltwiki.org/http://ltwiki.org/http://ltwiki.org/http://www.linear.com/designtools/software/


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Next week: Zener Diodes

Are there any questions?

To the right:A Google search for zener diode testing

found a pdf with this image. YMMV!

Documents

ECE3254 Lab01 Diodes Notes (2)