# The Invention of the Junction Transistor

> William Shockley's 1951 patent for the junction transistor, the fundamental building block of all modern digital electronics.

- **Patent:** US 2569347
- **Original title:** Circuit element utilizing semiconductive material
- **Owner:** Bell Telephone Laboratories Inc
- **Granted:** 1951
- **Status:** Public domain (expired)
- **Times cited:** 145
- **Field:** semiconductors, telecommunications, consumer_electronics

## What it does

This patent describes a three-layer semiconductor device, known as a junction transistor, which acts as an electronic switch or amplifier. By sandwiching a thin layer of one type of semiconductive material between two layers of the opposite type, the device controls the flow of electrical current. This allows a small input signal to regulate a much larger output current, effectively mimicking the function of bulky vacuum tubes in a tiny, solid-state package.

## What it does NOT cover

- Does not cover the earlier point-contact transistor design developed by Bardeen and Brattain.
- Does not cover field-effect transistors (FETs) that rely on a gate-controlled electric field rather than p-n junctions.
- Does not cover integrated circuits or the process of etching multiple transistors onto a single silicon wafer.

## The clever bit

The genius was in using the 'junction'—the interface between p-type and n-type semiconductor materials—to precisely control charge carrier injection, rather than relying on the unpredictable surface contact points of previous designs.

## Real-world examples

1. Early transistor radios
2. Mainframe computer processors
3. Modern silicon-based logic gates

## Why it matters

This patent is the cornerstone of the information age. It replaced fragile, power-hungry vacuum tubes with reliable, efficient semiconductor switches, enabling the miniaturization of everything from hearing aids to the supercomputers that power the modern internet.

## Frequently asked questions

### What does The Invention of the Junction Transistor cover?

William Shockley's 1951 patent for the junction transistor, the fundamental building block of all modern digital electronics.

### Who owns patent US 2569347?

Bell Telephone Laboratories Inc owns this patent, granted in 1951.

### When does this patent expire?

This patent has expired and is now in the public domain — anyone can use the invention freely.

### What is patent US 2569347 cited by?

This patent has been cited by 145 later patents that build on its ideas.

### What problem does this patent solve?

This patent is the cornerstone of the information age. It replaced fragile, power-hungry vacuum tubes with reliable, efficient semiconductor switches, enabling the miniaturization of everything from hearing aids to the supercomputers that power the modern internet.

### What does this patent NOT cover?

Does not cover the earlier point-contact transistor design developed by Bardeen and Brattain.

**Full plain-English explainer:** https://patentbrief.org/patent/us/2569347/junction-transistor

**Original patent:** https://patents.google.com/patent/US2569347

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._


## Related patents

Semantically similar inventions in the PatentBrief corpus:

- [The Invention of the Transistor](https://patentbrief.org/patent/us/2524035/point-contact-transistor) — Bell Labs' 1950 patent for the point-contact transistor, the fundamental electronic component that makes all modern computing possible.
- [The Invention of the Modern Field-Effect Transistor](https://patentbrief.org/patent/us/3102230/mosfet-field-effect-transistor) — This 1960 patent describes the fundamental structure of the MOSFET, the tiny electronic switch that powers every modern computer processor.
- [How the First Infrared LED Was Invented](https://patentbrief.org/patent/us/3293513/infrared-led-biard-pittman) — Texas Instruments' 1962 patent for the first practical semiconductor diode that emits infrared light when electricity passes through it.
- [How the First Practical Silicon Solar Cell Works](https://patentbrief.org/patent/us/2780765/solar-cell-photovoltaic) — A 1954 invention by Bell Labs researchers that created the first silicon-based solar cell capable of converting sunlight into enough electricity to power everyday devices.
- [How Jack Kilby Invented the First Integrated Circuit](https://patentbrief.org/patent/us/3138743/kilby-monolithic-integrated-circuit) — Texas Instruments' 1959 patent for the first integrated circuit, which combined transistors and resistors on a single piece of semiconductor material.