Made for the U.S. Army, this late 1950s / early 1960s film features the fundamental principles of diodes and triodes. It was presented by The Bray Studios Incorporated (:11). It opens with diode fundamentals (:28) showing electron components comprised of semiconductor material (:34). A transistor (:42) is an amplifier serving with the same purpose as a triode vacuum tube. A crystal rectifier is shown (:51). A circuit is demonstrated to conduct current in a single direction (1:18) as a light bulb is lit. When the voltage is reversed, the light bulb remains off (1:25). Animation shows how the crystal of the crystal rectifier (1:41) is composed of semiconductor material such as silicon (1:49). A simple DC circuit is shown (2:17). Electrons within the wire current move towards the positive battery terminal (2:21). A close up shot shows the two halves types of the crystal (2:52) which have been chemically treated. One half of the material is called the N-type (3:06) and the other is the P-type (3:10). The N-type material (3:27). Foreign atoms are introduced and contribute free electrons to the crystal (3:46). These move about at high speeds (4:06). As the crystal is heated, the movement is increased (4:17) and it slows as the crystal cools (4:23). This rate of motion is thermal agitation (4:31). An example shows the whole crystal to be composed of N-type material (5:00). The current is seen flowing as voltage is applied (5:06). The crystals and wire contain free electrons (5:14). The other half of the material is zoomed in on (5:20). The P-type has also been chemically treated through the addition of atoms from another material (5:31). One positive particle is added by the foreign atoms (5:35). The free particles are referred to as holes (5:52). Holes act are positively charged (5:57) and are also thermally agitated (6:08). The positive side moves the holes towards the crystal in the opposing direction which the electrons would take (6:26). At the positive terminal, holes and electrons are formed in pairs (6:40). Electrons are seen moving through the wire as the positive particles move into the semiconductor (6:51). Holes meet at the negative terminal and then disappear in pairs (7:01). A demonstration follows depicting how the crystal acts as a rectifier (7:26). The PN junction is where the holes and the electrons meet (7:43). Holes are seen crossing into the N-type material (8:13) where they will encounter electrons (8:20). The charges combine and cancel one another out (8:28). Electrons are seen crossing into the P-type material (8:43) where they will meet and combine with holes (8:49). Disappearing particles are replaced by others entering the crystal (8:55). Forward voltage is applied and current flows (9:12). When reverse bias is applied, holes and electrons are moved to the terminals (9:24) resulting in no current flow. Triode fundamentals are then shown (10:28). When the cover is removed, three sections of a semiconductor crystal is seen (10:45). This may be either PNP transistors (11:07) or NPN transistors (11:16). Reverse bias is applied to the right hand PN junction (11:53) and no current flows. The collector circuit is the amplifier’s output circuit (12:13). The emitter base junction is the amplifiers input circuit (12:33). A forward bias enables electrons to cross the first junction (12:41). If the junction was thicker (12:58), no current moves across the base collector junction (13:12). When the base material is thin, electrons pass through avoiding holes (13:41). The collector terminal attracts holes across the collector junction (14:01). The emitter current of electrons crossing the junction (15:01). Electrons cross the second junction into the positive battery terminal (15:08). The collector current is electrons from the emitter (15:20). The collector current is determined by the voltage applied (15:28) and is controlled by the emitter voltage (15:34). Output voltage is increased (16:06). A high resistance load can be added in the output (16:47) providing a voltage drop. When the output voltage is bigger than the input voltage (17:04) there is amplification and power gain (17:09). Output voltage must be less than the bias voltage (17:45). When the voltage drops too low it cancels the collector bias voltage (17:50) and stops the action (17:57). An audio signal is added from a microphone (18:19). The output power could now be 150 times as large as the input (18:42). A Zenith Royal 760 compact transistor radio (18:59) as well as a digital computer with Nixie tubes (19:13) which appears to be a transistorized unit built by Bell Labs in the late-50’s. Some other applications are shown(19:18).

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