The Invention of the Junction Transistor
William Shockley's 1951 patent for the junction transistor, the fundamental building block of all modern digital electronics.
Original patent title: “Circuit element utilizing semiconductive material”
William Shockley's 1951 patent for the junction transistor, the fundamental building block of all modern digital electronics. Granted to Bell Telephone Laboratories Inc in 1951 with 145 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
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.
The gap
What does this patent 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
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.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Early transistor radios
Mainframe computer processors
Modern silicon-based logic gates
Why it matters
The bigger picture
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.
Filed
June 26, 1948
Granted
September 25, 1951
Market context
Who's building on this
Companies in this space
Every major semiconductor company, including Intel, TSMC, and Samsung, builds upon the foundational physics of the junction transistor described here. While the original patent has long expired, the principles of junction-based current control remain the bedrock of CMOS technology.
Market impact
This patent triggered the transition from analog vacuum-tube electronics to the digital solid-state era. It enabled the creation of the semiconductor industry, directly leading to the development of the microprocessor and the exponential growth of computing power described by Moore's Law.
Claim 1 — Plain English
What this patent covers
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.
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.
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.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Moderate
Citation count
40/40
Highly cited
Claim breadth
0/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$50K – $161K
Midpoint $101K · expired or expiring · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
Concepts involved
Citations
Patent lineage
Cite this patent
William, S. (1951). The Invention of the Junction Transistor (U.S. Patent No. 2,569,347). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/2569347/junction-transistor
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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The Invention of the Transistor
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Common Questions
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.
Same assignee
More from Bell Telephone Laboratories Inc
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