Smaller
than a thimble, more rugged and efficient than present tube designs, and
particularly suited for mechanized production, the "Nuvistor"
represents a radical departure in the electronic-tube concept. Developed by the
RCA Electron Tube Division, triode and tetrode versions have already been
demonstrated in TV tuners reduced to one third the volume of conventional tuners.
Although
transistors are still a "natural" for many low-level applications, the
Nuvistor does provide certain significant advantages:
Nuvistors,
being in the tube family, are high-impedance devices--circuit components are
generally less expensive.
Lower
noise figures and higher frequency operation are obtained.
Tubes
can handle momentary overloads while solid state devices generally will burn
out.
Stable
operation is possible with Nuvistors over wide temperature ranges (-190°C
to 350°C).
(Electronic
Design, April 15, 1959, p. 3)
1
Heater
10
wires
2
Cathode
Support
11
The complete
Nuvistor
3
Cathode
12
Electrodic
System mounted on Ceramic Basement
4
Grid
13
Metallic Ring
for Braising
5
Anode
6
Anode Ring
7
Grid Ring
8
Cathode Ring
9
Ceramic
Basement
The
Nuvistor, a miniature metal-envelope tube, was another major advance in
vacuum-tube technology, following on the heels of the cold-cathode tube.
Unfortunately, the release of the Nuvistor appeared in the same issue as the
announcement of the first integrated circuit, and its fate was all but sealed
right from the start.--Steve Scrupski
The 6CW4 Nuvistor
Propped
up on the 50p are a couple of Nuvistors. These are metal clad thermionic
valves which were available in various guises, such as triodes (these
examples) or tetrodes etc. The valve, introduced by RCA in 1959 is claimed
to be the smallest ever made.
They have 6.3 volt heaters
and have lower than normal HT requirements.
Noise performance was
excellent and has only been relatively recently been surpassed by
transistors. The latter are now far superior to valves with noise figures
typically of around 0.5dB at 12GHz but in the early days of transistors
the nuvistor was the only real option if one wanted good performance at
VHF and UHF. That is unless one wanted to spend pots of money on really
exotic devices such as parametric amplifiers and the like.
The 6CW4 being a triode
was not too easy to use to obtain its maximum performance as it needed to
be neutralised; that is to balance out internal feedback to prevent it
oscillating. Not only was the nuvistor found in high performance VHF
receivers it was also used in the popular Tektronix oscilloscopes of the
60s in their wideband Y amplifiers were it happily co-existed with
transistors.