- Lee
De Forest -
Patent No: 879532
- The
Lee De Forest vacuum
valve was an
adaptation of the Sir
Ambrose Fleming (1905)
two element diode.
De Forest inserted a
third element in the
glass envelope that
acted as control grid.
This control element
regulated the flow of
electrons between the
cathode filament and
the anode plate. A
small change in
voltage on the control
grid forced a larger
change of current
flowing between the
cathode and anode and
hence providing the
worlds first signal
amplifier. Lee De
Forest applied for the
patent on 29th January
1907, it was
awarded to him 18th
February 1908.
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