OK, I'll 'fess up. The bipolar transistor was invented in 1947, as is
well known, but almost all modern electronics uses MOSFETS, which were
patented in 1928 by the brilliant Julius Lilenfield, who also patented
the junction FET in the same year.

However, the advance in solid-state amplifier techniques since that
time has been massively greater than that of the thermionic amplifier.
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Stewart Pinkerton | Music is Art - Audio is Engineering