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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

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
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Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
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Cied
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Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
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I start with an easy one. carbon nanotubes woven into a long filament like a string
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many many of nanotubes
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I'm interested in nanotube
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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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