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The current-voltage sweep is one of the fundamental experiments used to characterize the behavior of a diode. The Diode IV Sweep lab is designed as a laboratory or at-home experiment. Low cost National Instruments Data Acquisition products are used to excite and acquire data from the Diode-Resistor network.

Diode iv sweep using national instruments low cost data acquisition

Introduction

The diode is a basic circuit element that possesses nonlinear IV characteristics. In contrast to a simpleresistor, doubling diode current does not necessarily double the voltage across the diode. In order to visualize this nonlinearrelationship, it is common to plot diode current vs. voltage on a 2D graph. This graph can also be used at a later point to perform“load line” calculations on circuits with diodes.

In this exercise, the experimenter will construct a simple circuit to measure the IV characteristic of adiode. The Low Cost USB DAQ will be used as a programmable voltage source as well as an analog measurement device. The experimentaldata collected can be compared to expected theoretical data to draw conclusions regarding measurement noise, model shortcomings, anddata acquisition.

Pre-lab assignment

  • Research the exponential diode model using textbooks, the internet, or any other source. This model is more commonly referredto as the “ideal diode model”. What other diode models can you find?
  • What formula(s) can you find relating diode current and voltage? Note that the exponential, or “ideal diode model” shouldhave an exponential term.
  • Search Google for “Phillips 1N914” and open up the pdf datasheet. Find the graph of diode forward current vs voltage andnote your observations. Does the forward IV curve look exponential? How does the reverse IV curve look?
  • Use a simulation package such as Multisim to obtain the IV characteristic of a simulated diode. Do this by sweeping either the diode current or voltage, andmeasuring the other quantity.
  • Become familiar with the National Instruments USB 6008 and 6009 data acquisition devices. These datasheets are available on www.ni.com .

Theory

One commonly used method of modeling a diode is the “ideal diode model”. Using this model, diode voltage andcurrent are related according to the following formula:

Ideal Diode Model

Since Is is typically very small (1E-12), this equation is commonly simplified to:

Simplfied Diode Model Equation

Note that in the formula, Is stands for the saturation current which is around 1E-12 A, and Vt is a temperaturedependent constant equal to 0.0259 V at 300 degrees K. Id and Vd represent diode current and voltage respectively.

Therefore, a theoretical diode IV curve can be plotted using LabVIEW:

IV Curve plotted using LabVIEW

Hardware and software required

  • 10 Ohm resistor
  • Diode
  • National Instruments Low Cost USB DAQ
  • LabVIEW 8.20 software (LabVIEW 7.1 or 8.0 will work as well)

Labratory procedure

1) Construct the following circuit and connect to the USB 6008/6009. By outputting a certain voltage at AO 0 and measuring thevoltage at AI 3+, the experimenter can obtain a data point containing diode voltage and current. The diode voltage is simplythe voltage at node AI 3+, and the diode current is identical to the resistor current (Ohm’s Law).

Circuit for Measuring Diode IV Curve

2) Use a DMM to measure the actual resistance used for R1 in the circuit above (take R1 out of the circuit for measurement). This will help to obtain a moreaccurate current reading.

3) Using the DAQ Assistant Express VI, construct the following LabVIEW block diagram. Note that the userwill be able to select the number of IV data points to collect, as well as the ending sweep voltage for AO 0. Select this voltage lowenough to ensure that resistor R1 does not exceed its power specification.

LabVIEW Block Diagram Used to Measure Diode IV Curve

4) Run the VI several times using different values for the number of data points and sweep ending voltage.Record your observations and print out three diode IV curves with different numbers of data points.

Post-lab questions

  • Did the measured diode characteristic curve closely resemble what you expected? How closely did this curve match the datasheet,simulation, and theoretical data you researched earlier?
  • The measured IV curve may have contained some noise. Elaborate on some possible sources of this noise (think about yoursurroundings). Can you think of a way to eliminate some of the undesired noise from the signal? Would you do this in hardware orsoftware?
  • What real-world situations would require a designer to measure the diode characteristic curve?
  • What quantities could you measure for a bipolar junction transistor (BJT) using the low cost USB acquisition device? Explain how you would make your measurements.

Questions & Answers

List and explain four factors of production
Vuyo Reply
capital labour entrepreneur natural resources
Thembi
What is supply
Ogodo Reply
when the supply decreases demand also decreases
Thembi
types of demand and the explanation
akin Reply
what is demand
akin Reply
other things remaining same if demend is increases supply is also decrease and if demend is decrease supply is also increases is called the demand
Mian
if the demand increase supply also increases
Thembi
you are wrong this is the law of demand and not the definition
Tarasum
Demand is the willingness of buy and ability to buy in a specific time period in specific place. Mian you are saying law of demand but not in proper way. you have to keep studying more. because its very basic things in Economics.
Hamza
Demand is the price of Quantity goods and services in which consumer's are willing and able to offer at a price in the market over a period of time
Umar
what is commercialization?
Doris Reply
How to talk loan for bank?
Alfred Reply
what is the meaning of gpa?
Ritisha Reply
Answer: GPA stands for Grade Point Average. It is a standard way of measuring academic achievement in the U.S. Basically, it goes as follows: Each course is given a certain number of "units" or "credits", depending on the content of the course.
Yusuf
what is small and Microbuisenes
tadesse Reply
What is fiscal policy
Dansofo
Who is the funder of Economic
Dansofo
founder , that is Adam Smith
Daniel
what is model
Daniel Reply
The wealth of Nations
Yusuf Reply
the wealth of nations, is it the first?
Umar
Yes very sure it was released in 1759
Yusuf
thank you Yusuf.
Umar
then when did he died?
Umar
17 July 1790 Born: 16 June 1723, Kirkcaldy, United Kingdom Place of death: Panmure House, Edinburgh, United Kingdom
Yusuf
1790
Yusuf
that's my today questions, thank you Yusuf it's bed time see u after.
Umar
what is fiscal policy
kemigisha Reply
what's mode?
Umar Reply
mode is the highest occurring frequency in a distribution
Bola
mode is the most commonly occurring item in a set of data.
Umar
Please, what is the difference between monopoly and monopsony?
Olaleye Reply
is there monopsony word?
Umar
I have no idea though
Umar
please, in which year Adam smith was born?
Umar
monopsony is when there's only one buyer while monopoly is when there's only one producer.
Bola
who have idea on Banter
Ibrahim
like trade by barter?
Bola
Monopoly is when there's excessively one seller and there is no entry in the market while monopsony is when there is one buyer
kemigisha
Adam smith was born in 1723
Bola
 (uncountable) Good humoured, playful, typically spontaneous conversation. verb (intransitive) To engage in banter or playful conversation. (intransitive) To play or do something amusing. (transitive) To tease mildly.
Umar
which book Adam smith published first? the first book of Adam smith pls.
Umar
wealth on nation, 1776
Daniel
what is market power and how can it affect an economy?
Gab Reply
market power:- where a firm is said to be a price setter.market power benefits the powerful at the expense of others.
Umar
Market power refers to the ability of a firm (or group of firms) to raise and maintain price above the level that would prevail under competition is referred to as market or monopoly power. The exercise of market power leads to reduced output and loss of economic welfare
Kartheek
find information about the national budget
Molahlegi
three branches of economics in which tourism is likely to figure
Makgotso Reply
What are those three branches?
IlRegno
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Source:  OpenStax, Electronics experiments using usb data acquisition. OpenStax CNX. Dec 15, 2006 Download for free at http://cnx.org/content/col10393/1.1
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