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The Transistor Logic Gate
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27. ágúst 2026SE
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The Transistor Logic Gate

Every limit in this batch has been physical rather than logical. The relay was correct and took milliseconds because it had to move metal. The valve switched a thousand times faster and burned a heater continuously, so a machine with eighteen thousand of them consumed a house’s worth of power and failed somewhere every few hours. The transistor, already in this catalogue, does the same switching with no moving part, no heater, and a fraction of the power — and it is small enough that thousands fit where one valve stood. Nothing in the logic changes at all: the gates are the same gates Shannon described in 1937 and the arithmetic is the same arithmetic. What changes is that they become cheap enough to use in quantities that make the previous chapters look like sketches.
Miðlungs
5 hours 30 minutes

Leiðbeiningar

1

Build the same three gates, a thousand times faster

Rebuild the relay blueprint's gates with transistors and compare them directly.

  1. NOT: one NPN transistor, base through a resistor to the input, collector through a resistor to supply. Output at the collector.
  2. NOR: two transistors sharing one collector resistor — either input high pulls the output low.
  3. NAND: two transistors in SERIES — both inputs must be high to pull the output low.
  4. Verify each truth table, then measure propagation delay with the oscilloscope.

Series is AND and parallel is OR, exactly as with relay contacts — the topology did not change, only what is doing the switching. The delay will be tens of nanoseconds against the relay's milliseconds.

Note that the natural transistor gates are the INVERTING ones — NAND and NOR — because a transistor pulls its output DOWN when driven. A non-inverting AND costs an extra inverter. That is why real logic families are built from NAND and NOR, and why the next step matters so much.

Efni fyrir þetta skref:

Transistor Assortment (NPN/PNP)Transistor Assortment (NPN/PNP)1 sett
Resistor KitResistor Kit1 sett
LED Indicator SetLED Indicator Set1 sett
Perfboard / ProtoboardPerfboard / Protoboard1 stykki
Hookup Wire (22 AWG)Hookup Wire (22 AWG)1 reel

Nauðsynleg verkfæri:

Soldering Station (Temperature Controlled)Soldering Station (Temperature Controlled)
Oscilloscope 2-Channel 100MHzOscilloscope 2-Channel 100MHz
Function Generator 10MHzFunction Generator 10MHz
Digital Multimeter (Lab Grade)Digital Multimeter (Lab Grade)
Adjustable Bench Power Supply (30V/5A)Adjustable Bench Power Supply (30V/5A)
2

NAND is enough for everything

Blockly vinnusvæði

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Nauðsynleg verkfæri:

Desktop ComputerDesktop Computer
3

Fan-out, noise margin and why digital is reliable

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Nauðsynleg verkfæri:

Desktop ComputerDesktop Computer
4

Measure the power, and find the real wall

The valve machine's limit was heat. Measure whether that limit really went away.

  1. Measure the current your transistor gate draws with the output high, and again with it low.
  2. Now drive it with a square wave and measure average current against frequency.
  3. Plot it and extrapolate.

Static current is small; average current rises roughly in proportion to switching frequency, because every transition charges and discharges the capacitance of the next stage, and that energy is dissipated as heat every single time.

So the heat problem never disappeared — it was postponed, and it returns the moment you have enough gates switching fast enough. That is precisely the wall processors hit around 2005, when clock speeds stopped rising and manufacturers began adding cores instead: not because faster was impossible, but because the heat was.

CMOS was the escape from the static half of the problem — it draws almost no current when it is not switching, which is why it displaced everything else and why a modern chip's power is almost entirely switching energy. ENIAC's engineers left their valves powered continuously because switching them on and off killed them; the same instinct, for a different reason, is why your phone aggressively idles its cores.

Efni fyrir þetta skref:

Transistor Assortment (NPN/PNP)Transistor Assortment (NPN/PNP)1 sett
Resistor KitResistor Kit1 sett
Capacitor KitCapacitor Kit1 sett

Nauðsynleg verkfæri:

Oscilloscope 2-Channel 100MHzOscilloscope 2-Channel 100MHz
Function Generator 10MHzFunction Generator 10MHz
Digital Multimeter (Lab Grade)Digital Multimeter (Lab Grade)
Current Clamp Meter AC/DC 600ACurrent Clamp Meter AC/DC 600A
Adjustable Bench Power Supply (30V/5A)Adjustable Bench Power Supply (30V/5A)
5

Assemble the batch into a computer

Everything needed has now been built. Put it together and notice that nothing is missing.

  1. Gates — from this blueprint, or from relays if you prefer to hear it working.
  2. An adder — from the binary adder blueprint.
  3. Registers — flip-flops from the Eccles-Jordan blueprint.
  4. Memory — core, or simply more flip-flops at small scale.
  5. A program counter, an instruction decoder and a conditional jump — from the stored-program blueprint.
  6. An assembler — from the previous blueprint, to make it usable by a human.

That is a complete general-purpose computer, and every part of it was invented before 1950. Everything since has been the same architecture made smaller, faster and cheaper — which is not a small thing, since it changed the world, but it is not a different thing.

The batch's real lesson is the one it has repeated at every step: the logic was finished in 1937 and the engineering was never finished at all. Shannon's algebra describes a relay machine, a valve machine, a transistor machine and the processor rendering this page, without alteration. What changed a million-fold, twice, was the switch — and each time the switch improved, the same ideas simply became affordable in larger quantities. If you want to know what computing does next, do not look at the algebra. Look at what is replacing the transistor.

Nauðsynleg verkfæri:

Desktop ComputerDesktop Computer

Efni

6

Nauðsynleg verkfæri

7

CC0 opinbert ríki

Þessi teikning er gefin út undir CC0. Þér er frjálst að afrita, breyta, dreifa og nota þetta verk í hvaða tilgangi sem er, án þess að biðja um leyfi.

Studdu smiðinn með því að kaupa vörur í gegnum teikningu hans þar sem hann fær þóknun smiða sem seljendur ákvarða, eða búðu til nýja endurskoðun á þessari teikningu og tengdu hana sem tengingu í þinni eigin teikningu til að deila tekjum.

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