Battery (vacuum tube)


Battery (vacuum tube)

In electronics, vacuum tubes were traditionally powered by batteries. Each battery had a different designation depending on which vacuum tube element it was associated with.

Initially, the only such device was a diode with only a filament (cathode) and a plate (anode). Following the direction of electron flow, these electrodes were identified as "A" and "B", respectively and thus the associated batteries were referred to as the "A" battery and "B" battery, respectively. Later, when the control grid element was added to create the triode tube, it was logically assigned the letter "C" and supplied from a "C" battery. Subsequent addition of further internal elements to improve the performance of the triode, did not require an extension to this series of batteries - these elements were either resistively-biased from the existing batteries, connected to ground or to the cathode.

A battery

An A battery is any battery used to provide power to the filament of a vacuum tube. It is sometimes colloquially referred to as a "wet battery" (although there's no reason why a "dry" battery of suitable voltage couldn't be utilised for the purpose; the A battery in the photo is a dry battery.) The term comes from the days of valve (tube) radios when it was common practice to use a dry battery for the plate (Anode) voltage and a rechargeable lead/acid "wet" battery for the filament voltage. (The filaments in vacuum tubes consumed much more current than the anodes, and so the "A" battery would drain much more rapidly than the "B" battery; therefore, using a rechargeable "A" battery in this role reduced the need for battery replacement. In contrast, a nonrechargeable "B" battery would need to replaced relatively infrequently.)

The prior existence of the "A" battery is apparently the reason why there is no single-A battery (cell) size, just AA and AAA. In devising the lettered sizes for single-cell "batteries," it seems that there was a conscious effort to avoid single-A, while the omission of "B" was likely due to its association with a much higher voltage.

B battery

A B battery is any battery used to provide the plate voltage of a vacuum tube. It is sometimes colloquially referred to as a "dry battery" (although there's no reason why a "wet" battery of suitable voltage couldn't be utilised for the purpose).

The filament is primarily a heat source and therefore the A Battery supplies significant current and rapidly discharges. The B battery experiences comparatively little current draw and retains its stored capacity far longer than an A Battery. The voltage on a B Battery was typically 90V DC and often tapped to provide a lower voltage for screen grids or other purposes.

Even when the plate voltage rail is fed by a power supply rather than a battery, it is generally referred to as the "B+" line.

The prior existence of the "B" battery is apparently the reason why there is no B-size single-cell "battery." In devising the lettered sizes it seems that there was a conscious effort to avoid "B," possibly also due to its association with a much higher voltage. Single-A was also avoided, but there was apparently no concern for possible confusion with the use of "C" as a size.

Because plate voltages can be as high as 300V DC, multiple B batteries may be connected together in series to additively provide the required operating voltages.

The much higher available voltage of B batteries means that they must be handled more carefully than other battery types due to their ability to shock and/or burn the person handling them. With common flashlight cells, the normal resistance of the human body is far too high for much current to flow, but the shock hazard increases as the voltage increases.

C battery

In electronics, a C battery is any battery used to provide bias to the control grid of a vacuum tube. Until the early 1930s this was common practice in valve (tube) radio sets but was largely superseded by grid leak resistors or voltage divider biasing.

Grid bias batteries are still manufactured today, but not for radio use. They are popular in schools and colleges as a convenient variable voltage source in science classes. The most popular battery is the 9 volt type with taps every 1½ volts that accept a banana plug.

The "C" (grid) battery is not to be confused with the C cell. In devising the lettered sizes for single-cell "batteries," it seems that there was a conscious effort to avoid "B" due to its association with a much higher voltage, and single-A was also avoided, but there was apparently no concern for possible confusion with the use of "C" as a size. This may have been because C batteries typically had voltages below 10 volts (as low as 1.5 V, the voltage of modern "C" size cells), and because C batteries typically had multiple taps, making them obviously distinct from the modern "C" size cell, which has only two terminals.

External links

* [http://users.erols.com/radiola/C51man.htm Instructions for Operating The Crosley 51 Radio Receiver] Examples of usage of A, B, and C batteries in an early radio.


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Vacuum tube — This article is about the electronic device. For experiments in an evacuated pipe, see free fall. For the transport system, see pneumatic tube. Modern vacuum tubes, mostly miniature style In electronics, a vacuum tube, electron tube (in North… …   Wikipedia

  • Battery (electricity) — For other uses, see Battery (disambiguation). Various cells and batteries (top left to bottom right): two AA, one D, one handheld ham radio battery, two 9 volt (PP3), two AAA, one C, one …   Wikipedia

  • Battery eliminator — A battery eliminator is a device powered by an electrical source other than a battery, which then converts the source to a suitable DC voltage that may be used by a second device designed to be powered by batteries. A battery eliminator does away …   Wikipedia

  • Tube socket — Left to right: octal (top and bottom view), loctal, and miniature (top and side view) sockets. An early transistor socket and an IC socket are included for comparison. Tube sockets are electrical sockets into which vacuum tubes (also known as… …   Wikipedia

  • Vacuum fluorescent display — A vacuum fluorescent display (VFD) is a display device used commonly on consumer electronics equipment such as video cassette recorders, car radios, and microwave ovens. Unlike liquid crystal displays, a VFD emits a very bright light with clear… …   Wikipedia

  • Vacuum cleaner — Cylinder vacuum cleaner for home use. French train vacuum cleaner …   Wikipedia

  • List of battery sizes — 4.5 Volt, D, C, AA, AAA, AAAA, A23, 9 Volt, CR2032 and LR44 batteries. This article lists the sizes and shapes of some common primary and secondary battery types in household and light industrial use. The long history of disposable dry cells… …   Wikipedia

  • List of vacuum tubes — This is a list of vacuum tubes or thermionic valves. Before the advent of semiconductor devices, hundreds of tube types were used in consumer and industrial electronics; today only a few types are still used in specialized applications. Contents… …   Wikipedia

  • B battery — noun battery for supplying a constant positive voltage to the plate of a vacuum tube • Hypernyms: ↑battery, ↑electric battery * * * ˈbēˌ noun Usage: usually capitalized 1st B : an electric battery connected in the plate circuit of an electron… …   Useful english dictionary

  • C battery — noun battery used to maintain the grid potential in a vacuum tube • Hypernyms: ↑battery, ↑electric battery * * * noun Usage: usually capitalized C : a battery used to maintain the potential of a grid controlled electron tube at a desired value,… …   Useful english dictionary


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.