From Garry J. Tee, University of Auckland
Auckland, New Zealand
The Examiner at the British Patent Office was not the first to discover the
significance of the FET (or NPN transistor), patented by Julius Lilienfeld on 28
January 1930 as US Patent 1745175.
Feedback asserted (1 March) that: “It is now too late to find out whether the
inventor was just an armchair dreamer, or succeeded in making a working FET.”
But that entire Patent 1745175 was reproduced by the US patent attorney Theodore
L. Thomas, in his memorable article “The twenty lost years of solid-state
physics”, published in ANALOG Science Fact—Science Fiction, March
1965. Thomas explained that Lilienfeld was a professor at the University of
Leipzig, and that he filed that patent application in Canada on 22 October 1925
and in the US on 26 October 1926.
The US patent gave Lilienfeld’s address as Brooklyn, and Thomas told that
Lilienfeld became a citizen of the US in 1935 and that he died in 1963.
Furthermore, Lilienfeld was granted the US Patent 1877140 on 13 September 1932
for an amplifier for electric currents, which Thomas interpreted as NPPN and
PNNP transistors; and Lilienfeld was also granted the US Patent 1900018 on 7
March 1933 for another NPN transistor, and for a reversed biased P-N junction
used as a variable capacitor.
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Lilienfeld’s attempted explanations of how his devices operated are
wrong—but that did not affect the validity of his patents. On 3 October
1950, the US Patent Office granted 3 patents, all with the title
“Three-Electrode Circuit Element Utilizing Semiconductive Materials”. In
particular, Patent 2524035 included a theoretical explanation of how a
transistor operated—which could not have been done when Lilienfeld was
granted his patents.
In 1956 the Nobel Prize for Physics was awarded to the team of US physicists
whose work was patented in 1950. In his 1965 article, Thomas asked the awkward
question—how could it have been possible for Lilienfeld’s patents to be
overlooked?
