Posts Tagged ‘Circuits’

SPICE it up – Circuit Simulation using LTspice

spice_it_up

Probably the most neglected, yet most useful, tool for circuit designers is SPICE.  SPICE gives you the luxury of simulating circuits to predict the results prior to building a physical circuit.  Being able to change resistor values or transistor configurations within a couple mouse clicks and a few keyboard presses, is a very powerful and time/money saving feature.  As such, it is also very useful in troubleshooting previously built circuits to find solutions to lingering design problems.

SPICE (Simulation Program with Integrated Circuit Emphasis) is open-source software released under the “BSD license”.  Several companies produce their own version of SPICE, such as TINA from DesignSoft or PSpice from Cadence.  However, the fastest and most user friendly implementation is LTspice.  LTspice is provided by Linear Technology and is completely free to use without restriction.  It is the same software that is used internally at Linear Tech to develop and test their line of analog/linear semiconductor ICs.  It was written by Mike Engelhardt, who periodically goes on tour teaching classes and answering detailed questions for his own software.

I’ll be holding a class to introduce the basics of using LTspice.  LTspice was originally written for Windows and was recently ported to Mac OS X.  The Windows version is capable of being run on Linux through Wine, but it obviously doesn’t run as well as on a native Windows machine.  I’ll be teaching with the Windows version, since I am the most familiar with it.  The Mac version has a slightly different user interface, but it shouldn’t be too difficult to keep up.  Here are the topics I’ll be covering:

  1. Placing & Wiring Up Components
  2. The Most Basic Simulation: DC Operating Point
  3. Labels and “Net” Names
  4. Finding Frequency Response: AC Sweep
  5. Using the Plot Window
  6. The Real Deal: Time-Domain Simulation (Transient Analysis)
  7. Piece-Wise Linear (PWL) Sources
  8. Using SPICE “Directives”
  9. Working with Semiconductors
  10. Linear Tech’s IC Models and Test Jigs
  11. Importing 3rd Party Models & Sub-circuits

 

The Details:

  • Who: Anyone who wants to learn LTspice (Open to the Public).  Some circuit knowledge is required.
  • When: Sunday, September 28th – 2:00pm to 4:00pm
  • Where: 3519 N. Elston – 2nd Floor in the Electronics Lab
  • Cost: FREE

 

18

09 2014

DC Circuits Class Notes

DC_circuits

Thanks to everyone who came and participated in the circuits class this past weekend.  There was a lot of material that was covered and there was no way to go through it all in exhausting detail.  So I’m making available a scanned PDF of the notes I wrote for the class.  Enjoy all the spelling errors, in addition to the one found above.  The edges might be cut-off in some areas, but it’s the best I can do:   DC_Circuits_SK

Also, Carl Karsten did the exhausting (and usually thankless) job of recording a video of the class.  It can be found here:

http://videos.pumpingstationone.org/video/32/basic-electronics-dc-circuits-class

The solution to the bonus question was never explicitly stated in the video, so here it is:

bonus_solution

 

 

05

07 2014

Basic Electronics – DC Circuits Class – Sunday June 29th @ 2pm

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Well, I finally got around to finishing the curriculum for a beginning Electronics class.  This class will cover a lot of the fundamentals that should be known when designing any type of electronic circuit.  DC circuits will be covered here, so no frequency dependent (AC) topics will be touched.  Hopefully in the future, I’ll have time to eventually write a followup Intermediate Electronics class that will cover AC circuits.

It will be broken up into two parts, a lecture-ish part with lots of fun whiteboard time and a lab (hands-on) portion:

Lecture Topics:

  1. Electricity, conductors, and insulators
  2. Ohm’s Law
  3. KVL & KCL: Series and Parallel circuits
  4. Voltage Dividers
  5. Traditional Circuit Analysis: Mesh Currents & Node Voltage
  6. Better Analysis Tools: Superposition & Thevenin’s Theorem
  7. Silicon Diodes and LEDs

Lab Topics:

  1. DC Circuit Simulation with LTspice (the best analysis tool)
  2. Learn how to use solderless breadboards
  3. Build simple circuits using resistors and LEDs

I will be giving away one small electronics “starter kit” consisting of a solderless breadboard, bags of resistors and capacitors, a bunch of jumper wires, and a digital multimeter.  I’ll most likely dish this kit out by asking a bonus question and giving it away to the first person with the correct answer.  Anyway, hope to see you there!

The Details:

  • Who: Anyone who knows basic Algebra (Open to the Public)
  • When: Sunday, June 29th – 2:00pm to 4:00pm…..or 5pm or 6pm or however long you wanna stay and learn
  • Where: 3519 N. Elston – 2nd Floor in the Electronics Lab
  • Cost: FREE

 

26

06 2014

Silicon ReSEMblance

Every year, the UIUC chapter of ACM has an student-run conference called Reflections|Projections . One (rather excellent) speaker at the 2013 conference was the well-spoken (and wickedly-smart) Todd Fernandez , who spoke about the state of the semiconductor integrated circuit industry. As a nice bonus for those brave souls who asked, or answered, a question during his talk, he was giving out junked silicon wafers. Not being much of a brave soul myself, but realizing that the wafer would make for an awesome sample in our now-functioning Scanning Electron Microscope (SEM), I answered a question about Moore’s Law and scored a wafer.

img_0007

Here’s a picture of a similar wafer we had on hand (Not the one we put in the SEM. We shattered that one.)

Saving you a trip to Wikipedia: the wafers are slices of an impressively large and pure single crystal of silicon (known as a boule) on which semiconductor devices (such as transistors) are fabricated. These devices are usually incredibly tiny and incredibly numerous.

What happens after that is that the SEM rasters a beam of electrons across the surface of the wafer sample and, in this particular case, utilizes its ability to detect secondary electrons kicked off the wafer by the beam. Because the surface is the important part and because the SEM’s resolution is so amazing, before we mounted the sample, we had to sterilize it in an acetone bath suspended in the space’s ultrasonic cleaner.

 

Now the cool part. Because, if you look at the picture below, you can easily see leads on the wafer that are 4 microns in width (and resolve gaps between the leads that are 2 microns wide). For reference’s sake, the diameter of a human hair is given as 100 microns on average. And that is awesome.

sem003

Many thanks to the exceptional Ryan Pierce, who helped me with this every step of the way.

 

-Jerry Lebedowych

22

11 2013