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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


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 .


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

find the 15th term of the geometric sequince whose first is 18 and last term of 387
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The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
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I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
is it a question of log
Commplementary angles
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or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
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Differences Between Laspeyres and Paasche Indices
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In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
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Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
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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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