The TRANSISTOR DE-PUZZLER ©

by Mike Fitzsimmons

Using a common puzzle to solve the puzzle of how transistors work!

updated 2022-07-30
These web pages describe a technique I've used to teach people of almost all ages how transistors operate.
I realize that a lot more work is needed, but I'm releasing what I have so far.
Please contact me if interested in collaborating on a new video.

photo from an attempt to make a video a long time ago.

Video

Over a decade ago, I attempted to make a video, but I wasn't satisfied with my "acting" ability (too monotone and I didn't smile enough!), plus the video editors I tried were not as easy to use as I hoped (e.g. making stop-motion/claymation). 
Although I still might try making a better video myself, here is a web version (slightly edited) of the video script which ran about 6 minutes.  Go ahead and make your own version if you'd like!  I might even help if you ask.

Quick non-video Overview

Most forms of transistors involve some trick to get electric current to go through two back to back diodes.  Diodes only conduct in one direction (forward) as shown below.  One of the two back to back diodes will always be in backward non-conducting direction and therefore, block the flow of current.  It's just as important to know why a transistor can stop the flow of current as which of the tricks are used to turn the flow of electricity on.

Unlike common metals, semiconductors can be made to conduct electricity by having "missing" electrons called "holes" act as the charge carriers.  All it takes is a small number of atoms with one less electron in their outer shell to be the dominant impurity in a region of the crystal.  The resulting holes act like positive charge carriers and move like the space in the dime-store puzzles with one square missing.  The important thing is that they go in the opposite direction of electrons that carry the electric current in any area dominated by impurity atoms that have one extra electron than the silicon crystal.  The border between these two types of regions will be devoid of charge carriers if the applied voltage makes type of carrier go away from the junction.  Switch the voltage polarity and both types of charge carriers will be forced to meet at the junction where they cancel each other out. 

The most common transistors on this planet at this time uses the surface to bypass a pair of back to back transistors and get the overall structure to conduct electricity depending on the voltage at a third terminal as shown below. 

Next, we'll go through this in more detail.


What is a transistor?

The word transistor comes from the prefix "trans" (meaning across or change) modifying the word "resistor" (a two terminal electical device that resists the flow of electricity by a certain amount).  The ratio of an applied voltage to the electrical current it can push through a resistor is it's resistance value, R.  This value is fixed for a simple resistor, but not for a transistor.  Either the voltage or current at a third terminal changes the resistance of the other pair of terminals across a transistor.  The amount of energy needed to do the controlling is much much less than amount of energy being controlled.  That's what makes them so incredibly useful.  Transistors amplify electrical signals and in digital electronics they act as electrically controlled switches - either fully ON (low resistance) or fully OFF (high resistance). 


Under Construction.....but here are a couple photos that might be used.