Fix dollar signs + add descendants section

# [TECH] Transistor

**The Transistor** (1947, Bell Labs) is a semiconductor device that amplifies or switches electrical signals, replacing vacuum tubes and enabling the entire semiconductor industry.

## Overview

John Bardeen, Walter Brattain, and William Shockley demonstrated the point-contact transistor at Bell Labs (December 23, 1947). Shockley's bipolar junction transistor (1948) and the MOS field-effect transistor (MOSFET, Kahng & Atalla, 1960) followed. The MOSFET became the workhorse of integrated circuits — by 2023 approximately 10²² MOSFETs had been manufactured, more than any other human-made object. The transistor replaced vacuum tubes in radios and computers by 1960, enabling miniaturisation and reliability improvements of many orders of magnitude.

## Key Actors

- **Companies**: Bell Labs/AT&T (invention), Texas Instruments (first silicon transistor, 1954), Fairchild Semiconductor (1957), Intel (1968)
- **Inventors**: Bardeen, Brattain, Shockley (Nobel 1956); Dawon Kahng & Martin Atalla (MOSFET, 1959)

## Key Patents

- Shockley, W. US Patent 2,569,347 (1951) — junction transistor
- Kahng, D. & Atalla, M. US Patent 3,102,230 (1963) — MOSFET

## Economic Value

Global semiconductor market: **\$600 billion/year** (2023, WSTS). Electronics and computing enabled by transistors: \$5–8T/year. The transistor is possibly the most economically valuable invention of the 20th century.

## Notes

WSTS *Semiconductor Market Forecast* 2023. Some economists estimate the transistor's cumulative economic value at \$100T+ since 1950 when accounting for all electronics, communications, and computing it enabled.

## What This Enables
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- **[TECH] Integrated Circuit** — The transistor is the elementary switching and amplifying element from which all integrated circuits are built.
- **[TECH] Digital Computing** — Transistor-based logic (1950s–60s) replaced vacuum tubes, giving computers orders of magnitude better reliability and compactness.
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# Parents

* [SCI] Semiconductor Physics
* [TECH] Electric Power Grid
* [SCI] Theory of Metals
* [SCI] Semiconductor Physics