Discovering Transistors

My first-year group is just starting to explore transistors.  I’ve tried to improve my teaching of “how to read a data sheet.” Instead of reading them the data sheet for each new component, we’ve worked on identifying the common structure of all datasheets, understanding the patterns of organization, symbols, and terminology, and building a list of reputable resources (textbook, manufacturer/distributor websites, Google).  On Friday I introduced the conceptual language of amplifiers, using a worksheet that asks them to plot voltage vs. current and draw conclusions about the patterns.  Once we had explored how a transistor controls current, I asked them to build an LED driver and told them where the schematic was.  Then I walked away for 20 minutes.

2N3904 Transistor

The catch: I hadn’t shown them what a transistor looks like.

I hadn’t given them a copy of the datasheet and walked them through it.  I hadn’t even shown them where the datasheet was.  I went back, a bit anxious, wondering if I would have a mutiny on my hands.

The class was calmly working away, several of them experimenting with working LED drivers and asking themselves what else they could do with it.  They found the model number on the schematic, found the data sheet in the back of the lab book, used the picture to find the component in their component kits (in some cases supplemented by Google) and figured out for themselves how to map the symbol to the physical thing.

I walked around signing off skill sheets, silently relieved.  It’s working.

Also: when expecting students to do something conceptually tricky and self-directed… it helps if it rewards them with something that moves, blinks, or makes noise.

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