Skip to content Skip to navigation

Connexions

You are here: Home » Content » Diode IV Sweep Lab

Navigation

Lenses

What is a lens?

Definition of a lens

Lenses

A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual Connexions member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

This content is ...

Affiliated with (What does "Affiliated with" mean?)

This content is either by members of the organizations listed or about topics related to the organizations listed. Click each link to see a list of all content affiliated with the organization.
  • National Instruments display tagshide tags

    This module is included in aLens by: National InstrumentsAs a part of collection:"Electronics Experiments Using USB Data Acquisition"

    Comments:

    "This set of six student labs are designed to allow anyone to recreate simple experiments at home to explore electronics and electrical engineering concepts. The software and hardware utilized is […]"

    Click the "National Instruments" link to see all content affiliated with them.

    Click the tag icon tag icon to display tags associated with this content.

Recently Viewed

This feature requires Javascript to be enabled.

Tags

(What is a tag?)

These tags come from the endorsement, affiliation, and other lenses that include this content.

Diode IV Sweep Lab

Module by: Erik Luther, Casey Weltzin. E-mail the authors

User rating (How does the rating system work?)
Ratings

Ratings allow you to judge the quality of modules. If other users have ranked the module then its average rating is displayed below. Ratings are calculated on a scale from one star (Poor) to five stars (Excellent).

How to rate a module

Hover over the star that corresponds to the rating you wish to assign. Click on the star to add your rating. Your rating should be based on the quality of the content. You must have an account and be logged in to rate content.

:
(0 ratings)

Summary: 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 simple resistor, doubling diode current does not necessarily double the voltage across the diode. In order to visualize this nonlinear relationship, 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 a diode. The Low Cost USB DAQ will be used as a programmable voltage source as well as an analog measurement device. The experimental data collected can be compared to expected theoretical data to draw conclusions regarding measurement noise, model shortcomings, and data acquisition.

Pre-Lab Assignment

  1. Research the exponential diode model using textbooks, the internet, or any other source. This model is more commonly referred to as the “ideal diode model”. What other diode models can you find?
  2. What formula(s) can you find relating diode current and voltage? Note that the exponential, or “ideal diode model” should have an exponential term.
  3. Search Google for “Phillips 1N914” and open up the pdf datasheet. Find the graph of diode forward current vs voltage and note your observations. Does the forward IV curve look exponential? How does the reverse IV curve look?
  4. 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, and measuring the other quantity.
  5. 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 and current are related according to the following formula:

Figure 1: Ideal Diode Model
Figure 1 (Graphic1.png)

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

Figure 2: Simplfied Diode Model Equation
Figure 2 (Graphic2.png)

Note that in the formula, Is stands for the saturation current which is around 1E-12 A, and Vt is a temperature dependent 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:

Figure 3: IV Curve plotted using LabVIEW
Figure 3 (Graphic3.png)

Hardware and Software Required

  1. 10 Ohm resistor
  2. Diode
  3. National Instruments Low Cost USB DAQ
  4. 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 the voltage at AI 3+, the experimenter can obtain a data point containing diode voltage and current. The diode voltage is simply the voltage at node AI 3+, and the diode current is identical to the resistor current (Ohm’s Law).

Figure 4: Circuit for Measuring Diode IV Curve
Figure 4 (Graphic4.png)

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 more accurate current reading.

3) Using the DAQ Assistant Express VI, construct the following LabVIEW block diagram. Note that the user will 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 low enough to ensure that resistor R1 does not exceed its power specification.

Figure 5: LabVIEW Block Diagram Used to Measure Diode IV Curve
Figure 5 (Graphic6.png)

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

  1. 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?
  2. The measured IV curve may have contained some noise. Elaborate on some possible sources of this noise (think about your surroundings). Can you think of a way to eliminate some of the undesired noise from the signal? Would you do this in hardware or software?
  3. What real-world situations would require a designer to measure the diode characteristic curve?
  4. 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.

Content actions

Give Feedback:

E-mail the module authors | Rate module ( How does the rating system work?)

Rating system

Ratings

Ratings allow you to judge the quality of modules. If other users have ranked the module then its average rating is displayed below. Ratings are calculated on a scale from one star (Poor) to five stars (Excellent).

How to rate a module

Hover over the star that corresponds to the rating you wish to assign. Click on the star to add your rating. Your rating should be based on the quality of the content. You must have an account and be logged in to rate content.

(0 ratings)

Download:

Module PDF

Add module to:

My Favorites (?)

'My Favorites' is a special kind of lens which you can use to bookmark modules and collections directly in Connexions. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need a Connexions account to use 'My Favorites'.

| A lens (?)

Definition of a lens

Lenses

A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual Connexions member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

| External bookmarks