ever wonder why the schematic symbol of a bipolar transistor looks the way it does? the two angled lines look particularly odd, but there is a fascinating historical reason for it! 🧵 
first let's rotate the symbol 90 degrees so the base terminal is pointing down. still don't see it?
here's a photo of the first bipolar transistor. the semiconductor is a tiny sliver of germanium resting on a metal base. (yes, this is where the base terminal gets its name.)
and here's a page from Walter Brattain's lab notebook. this was an early test of the transistor's ability to amplify. note the little symbol he uses for the transistor!
here's a closeup. the triangle was a piece of plastic with a thin strip of gold foil glued to it. using a razor, Brattain's technician sliced the foil in two right at the very corner of the triangle, making the two closely-spaced emitter and collector contacts.
the transistor patent (2,524,035) uses a similar diagram but without the plastic triangle. now it's really starting to look like the familiar symbol!
the evolution of the transistor symbol becomes clear in a slightly later patent (2,585,078) by another Bell Labs researcher, Harold Barney.
(i can't go back and fix this, but i incorrectly identified the first transistor as bipolar when it is in fact a point-contact transistor. oops.)
IBM used a different symbol. this looks a lot more like a bipolar junction transistor!
