Transistor

The device Bardeen and Brattain built in December 1947 was a point-contact transistor: two gold contacts pressed on a germanium slab, with a small current gain and a habit of dying. Everything on this page (0.7 volts across the base junction, 0.2 volts when saturated, a gain of a hundred) describes the silicon bipolar junction transistor that came later. That is not what “transistor” means today either: almost every transistor now made is a MOSFET, which is voltage-controlled and has no base current to speak of, and the bipolar one is the transistor of a first course in electronics rather than of a modern chip. The date is right for the invention and wrong for the numbers, and it seemed better to say so than to publish a page nobody could compare with a datasheet.

Cut off below 0.7 volts, collector current equal to beta times base current above it, and a ceiling where the collector resistor cannot pass any more. That is enough to show the two facts this page is about and it is not enough for anything else: it has no temperature, no early effect, no leakage, and the transition between regions is a corner rather than a curve. A real device rounds every corner here.

Ohm's law works with no conversion factor in those units, which is deliberate: a stray factor of a thousand is exactly the kind of error that hides on a page like this and still looks plausible. Every number shown is computed from the three constants and the two resistor values, and the base current is never rounded before the collector current is derived from it.

No device was put on a bench for this. The numbers come out of the model, and the model comes out of a textbook. Where the page says the output never rises when the input does, that is a property of the model checked across the sweep when the page loads, not a measurement.

The first version of it said the transistor did “two things a relay cannot”, control a large current with a small one and invert, and called NOT “the gate relay contacts could not make”. Both halves are false. A relay coil switching a heavy contact load is exactly a small current controlling a large one, and a normally-closed contact opens when energised, which is inversion. Worse, Logical Art’s own Bitwise page says so in as many words: wire a contact so it opens when energised instead of closing, and you have NOT. The page had taken Bitwise’s point about XOR, which really is impossible with plain series and parallel make-contacts, and attached it to the wrong gate. An outside reader found it. The claim now rests on the continuous middle region, which a contact genuinely has no version of, and which is the thing this page draws.