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.
A VFD operates on the principle of cathodoluminescence, roughly
similar to a cathode ray tube, but operating at much lower voltages.
Each tube in a VFD has a phosphor coated anode that is bombarded by
electrons emitted from the cathode filament. In fact, each tube in
VFD is a triode vacuum tube because it also has a mesh control
Unlike liquid crystal displays, a VFD emits a very bright light with
high contrast and can support display elements of various colors.
Standard illumination figures for VFDs are around 640 cd/m2 with
high-brightness VFDs operating at 4,000 cd/m2, and experimental
units as high as 35,000 cd/m2 depending on the drive voltage and
its timing. The choice of color (which determines the nature of the
phosphor) and display brightness significantly affect the lifetime of
the tubes, which can range from as low as 1,500 hours for a vivid red
VFD to 30,000 hours for the more common green ones.
commonly used in VFDs in the past, but the current RoHS-compliant VFDs
have eliminated this metal from their construction.
VFDs can display seven-segment numerals, multi-segment alpha-numeric
characters or can be made in a dot-matrix to display different
alphanumeric characters and symbols. In practice, there is little
limit to the shape of the image that can be displayed: it depends
solely on the shape of phosphor on the anode(s).
The first VFD was the single indication DM160 by Philips in 1959.
The first multi-segment VFD was the 1962 Japanese single-digit,
seven-segment device. The displays became common on calculators and
other consumer electronics devices. In the late 1980s hundreds of
millions of units were made yearly.
2.1 Use as amplifier
5 See also
7 External links
Macro image of a VFD digit with 3 horizontal tungsten wires and
The device consists of a hot cathode (filaments), anodes (phosphor)
and grids encased in a glass envelope under a high vacuum condition.
The cathode is made up of fine tungsten wires, coated by alkaline
earth metal oxides, which emit electrons when heated by an electric
current. These electrons are controlled and diffused by the grids,
which are made up of thin metal. If electrons impinge on the
phosphor-coated plates, they fluoresce, emitting light. Unlike the
orange-glowing cathodes of traditional vacuum tubes, VFD cathodes are
efficient emitters at much lower temperatures, and are therefore
The principle of operation is identical to that of a vacuum tube
triode. Electrons can only reach (and "illuminate") a given plate
element if both the grid and the plate are at a positive potential
with respect to the cathode. This allows the displays to be
organized as multiplexed displays where the multiple grids and plates
form a matrix, minimizing the number of signal pins required. In the
example of the VCR display shown to the right, the grids are arranged
so that only one digit is illuminated at a time. All of the similar
plates in all of the digits (for example, all of the lower-left plates
in all of the digits) are connected in parallel. One by one, the
microprocessor driving the display enables a digit by placing a
positive voltage on that digit's grid and then placing a positive
voltage on the appropriate plates. Electrons flow through that digit's
grid and strike those plates that are at a positive potential. The
microprocessor cycles through illuminating the digits in this way at a
rate high enough to create the illusion of all digits glowing at once
via persistence of vision.
The extra indicators (in our example, "VCR", "Hi-Fi", "STEREO", "SAP",
etc.) are arranged as if they were segments of an additional digit or
two or extra segments of existing digits and are scanned using the
same multiplexed strategy as the real digits. Some of these extra
indicators may use a phosphor that emits a different color of light,
for example, orange.
The light emitted by most VFDs contains many colors and can often be
filtered to enhance the color saturation providing a deep green or
deep blue, depending on the whims of the product's designers.
Phosphors used in VFDs are different from those in cathode-ray
displays since they must emit acceptable brightness with only around
50 volts of electron energy, compared to several thousand volts in a
Besides brightness, VFDs have the advantages of being rugged,
inexpensive, and easily configured to display a wide variety of
customized messages, and unlike LCDs, VFDs are not limited by the
response time of rearranging liquid crystals and are thus able to
function normally in cold, even sub-zero, temperatures, making them
ideal for outdoor devices in cold climates. Early on, the main
disadvantage of such displays was their use of significantly more
power (0.2 watts) than a simple LCD. This was considered a significant
drawback for battery-operated equipment like calculators, so VFDs
ended up being used mainly in equipment powered by an AC supply or
heavy-duty rechargeable batteries.
A digital dashboard cluster in an American automobile.
During the 1980s, this display began to be used in automobiles,
especially where car makers were experimenting with digital displays
for vehicle instruments such as speedometers and odometers. A good
example of these were the high-end
Subaru cars made in the early 1980s
(referred to by
Subaru enthusiasts as a digi-dash, or digital
dashboard). The brightness of VFDs makes them well suited for use in
cars. Current models of Renault MPV, Scenic and Espace both use VFD
panels to show all functions on the dashboard including the radio and
multi message panel. They are bright enough to read in full sunlight
as well as dimmable for use at night. This panel uses four colors; the
usual blue/green as well as deep blue, red and yellow/orange.
This technology was also used from 1979 to the mid-1980s in portable
electronic game units. These games featured bright, clear displays but
the size of the largest vacuum tubes that could be manufactured
inexpensively kept the size of the displays quite small, often
requiring the use of magnifying Fresnel lenses. While
later games had sophisticated multi-color displays, early games
achieved color effects using transparent filters to change the color
of the (usually light blue) light emitted by the phosphors. High power
consumption and high manufacturing cost contributed to the demise of
the VFD as a videogame display.
LCD games could be manufactured for a
fraction of the price, did not require frequent changes of batteries
(or AC adapters) and were much more portable. Since the late 1990s,
backlit color active-matrix LCD displays have been able to cheaply
reproduce arbitrary images in any color, a marked advantage over
fixed-color, fixed-character VFDs. This is one of the main reasons for
the decline in popularity of VFDs, although they continue to be made.
Many low-cost DVD players still feature VFDs.
From the mid-1980s onwards, VFDs were used for applications requiring
smaller displays with high brightness specifications, though now the
adoption of high-brightness organic light-emitting diodes (OLEDs) is
pushing VFDs out of these markets.
In addition to the widely used fixed character VFD, a graphic type
made of an array of individually addressable pixels is also available.
These more sophisticated displays offer the flexibility of displaying
arbitrary images, and may still be a useful choice for some types of
Use as amplifier
Several radio amateurs have experimented with the possibilities of
using VFDs as triode amplifiers. In 2015,
Korg released the
Nutube, an analogue audio amplifier component based on VFD technology.
The Nutube is used in applications such as guitar amplifiers from
Vox and the Apex Sangaku headphone amplifier.
Fading is sometimes a problem with VFD displays. Light output drops
over time due to falling emission and reduction of phosphor
efficiency. How quickly and how far this falls depends on the
construction and operation of the VFD. In some equipment, loss of VFD
output can render the equipment inoperable.
Emission may usually be restored by raising filament voltage.
Thirty-three percent voltage boost can rectify moderate fade, and 66%
boost severe fade. This can make the filaments
visible in use, though the usual green-blue VFD filter helps reduce
any such red or orange light from the filament.
Some researchers suggest that "zapping" the phosphor and heater(s)
with selected laser wavelengths (patent pending) can restore some lost
emission by annealing the phosphor and exposing fresh heater electron
emitting material in some cases. A related approach appears to also
OLED displays by a different mechanism.
Of the three prevalent display technologies - VFD, LCD, and LED - the
VFD was the first to be developed. It was used in early handheld
calculators. LED displays displaced VFDs in this use as the very small
LEDs used required less power, thereby extending battery life, though
early LED displays had problems achieving uniform brightness levels
across all display segments. Later, LCDs displaced LEDs, offering even
lower power requirements.
The first VFD was the single indication DM160 by Philips in 1959. It
could easily be driven by transistors, so was aimed at computer
applications as it was easier to drive than a neon and had longer life
than a light bulb. This was made obsolete by LEDs. The 1962 Japanese
single digit seven segment display in terms of anode was more like the
Philips DM70 / DM71 Magic Eye as the DM160 has a spiral wire anode.
The Japanese seven segment VFD meant that no patent royalties needed
to be paid on desk calculator displays as would have been the case
using Nixies or Planaplex neon digits. In the UK the Philips designs
were made and marketed by Mullard (almost wholly owned by Philips even
The Russian ИВ-15 VFD tube is very similar to the DM160. The DM160,
DM70/DM71 and Russian ИВ-15 can (like a VFD panel) be used as
triodes. The DM160 is thus the smallest VFD and smallest triode valve.
The ИВ-15 is slightly different shape (see photo of DM160 and
ИВ-15 for comparison).
^ Shigeo Shionoya; William M. Yen (1998).
Phosphor Handbook. CRC
Press. p. 561. ISBN 978-0-8493-7560-6.
^ a b c Janglin Chen; Wayne Cranton; Mark Fihn (2011). Handbook of
Visual Display Technology. Springer. pp. 1056, 1067–1068.
^ (HB9RXQ), Ernst Erb. "DM 160, Tube DM160; Röhre DM 160 ID19445,
INDICATOR, in gene". www.radiomuseum.org.
^ Joseph A. Castellano (ed), Handbook of display technology Gulf
Professional Publishing, 1992 ISBN 0-12-163420-5 page 9
^ Joseph A. Castellano (ed), Handbook of display technology Gulf
Professional Publishing, 1992 ISBN 0-12-163420-5 page 176
^ Joseph A. Castellano (ed), Handbook of display technology, Gulf
Professional Publishing, 1992 ISBN 0-12-163420-5 Chapter 7 Vacuum
Fluorescent Displays pp. 163 and following
^ Elektrotechnik Tabellen Kommunikationselektronik (3rd ed.).
Braunschweig, Germany: Westermann. 1999. p. 110.
^ William M. Yen, Shigeo Shionoya, Hajime Yamamoto (editors) ,Phosphor
Handbook, CRC Press, 2007 ISBN 0-8493-3564-7 Chapter 8
^ N9WOS (29 July 2005). "VFD as an audio/RF amplifier?". Electronics
Point forums. Archived from the original on 11 March 2018. Retrieved
11 March 2018.
^ "H. P. Friedrichs, ''
Vacuum Fluorescent Display Amplifiers For
Primitive Radio'', ''eHam.net'' December 2008, retrieved 2010 Feb 8".
Eham.net. Retrieved 2012-12-11.
^ "Des. Kostryca, ''A VFD Receiver (Triodes in Disguise)'',
''eHam.net'' January 2009, retrieved 2010 Feb 8". Eham.net. Retrieved
^ "Vox MV50 AC guitar amplifier". Retrieved 11 March 2018.
^ "The Sangaku headphone amplifier". Retrieved 11 March 2018.
Wikimedia Commons has media related to
Vacuum fluorescent displays.
Noritake's Guide to VFD Operation
Vacuum Fluorescent Display (VFD) (including How to drive the filament)
Photos and specs for antique Russian VFD tubes
Simple VFD Test Circuit
The DM70 VFD related Magic eye
Triode and earliest VFD, the DM160, with size comparisons
The Russian VFD indicator like a DM160
Electroluminescent display (ELD)
Light emitting diode display (LED)
Cathode ray tube
Cathode ray tube (CRT) (Monoscope)
Liquid-crystal display (LCD)
Plasma display panel (PDP)
Digital Light Processing
Digital Light Processing (DLP)
Liquid crystal on silicon
Liquid crystal on silicon (LCoS)
Organic light-emitting diode
Organic light-emitting diode (OLED)
Organic light-emitting transistor (OLET)
Surface-conduction electron-emitter display
Surface-conduction electron-emitter display (SED)
Field emission display (FED)
Quantum dot display
Quantum dot display (QD-LED)
Ferro liquid crystal display (FLCD)
Thick-film dielectric electroluminescent technology (TDEL)
Telescopic pixel display (TPD)
Laser-powered phosphor display (LPD)
Vacuum fluorescent display (VFD)
Light-emitting electrochemical cell (LEC)
Seven-segment display (SSD)
Fourteen-segment display (FSD)
Sixteen-segment display (SISD)
History of display technology
Large-screen television technology
Optimum HDTV viewing distance
High-dynamic-range imaging (HDRI)
Color Light Output
Comparison of display technology