About the Nuvistor Triode

What's the Nuvistor?

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.