Bill uses a replica of the point contact transistor built by Walter Brattain and John Bardeen at Bell Labs. On December 23, 1947 they used this device to amplify the output of a microphone and thus started the microelectronics revolution that changed the world. He describes in detail why a transistor works by highlighting the uniqueness of semiconductors in being able to transfer charge by positive and negative carriers.
Bill is doing a great job with his video series, we are a fan!
The first transistor might not have been made in 1947, it probably happened earlier. If you search back in QST magazines from the 1920′s you will find many experimental hookups for ‘catwhisker’ crystal detectors. There were some that used TWO catwhiskers and a battery, with the claim of amplification. Could it be??? There was also a circuit using a single catwhisker and a battery for bias with the claim of regeneration. This was probably the very first example of a tunnel diode!