You can freely build on The Invention of the Junction Transistor

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.

What is now free to use

All 0 claims of US 2569347 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• 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.

Who is building on this today

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.

Products built on expired version of this technology

How to cite this patent in your documentation

Bell Telephone Laboratories Inc. US Patent 2569347. Circuit element utilizing semiconductive material. Granted 1951, expired 1968. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.