The LM3914 is a monolithic integrated circuit that senses analog voltage levels and
drives 10 LEDs, providing a linear analog display. A single pin changes the display from a moving
dot to a bar graph. Current drive to the LEDs is regulated and programmable, eliminating the need
for resistors. This feature is one that allows operation of the whole system from less than
The circuit contains its own adjustable reference and accurate 10-step voltage divider.
The low-bias-current input buffer accepts signals down to ground, or V−,
yet needs no protection against inputs of 35V above or below ground. The buffer drives 10
individual comparators referenced to the precision divider. Indication non-linearity can thus be
held typically to ½%, even over a wide temperature range.
Versatility was designed into the LM3914 so that controller, visual alarm, and expanded
scale functions are easily added on to the display system. The circuit can drive LEDs of many
colors, or low-current incandescent lamps. Many LM3914s can be “chained” to form displays of 20 to
over 100 segments. Both ends of the voltage divider are externally available so that 2 drivers can
be made into a zero-center meter.
The LM3914 is very easy to apply as an analog meter circuit. A 1.2V full-scale meter
requires only 1 resistor and a single 3V to 15V supply in addition to the 10 display LEDs. If the 1
resistor is a pot, it becomes the LED brightness control. The simplified block diagram illustrates
this extremely simple external circuitry.
When in the dot mode, there is a small amount of overlap or “fade” (about 1 mV) between
segments. This assures that at no time will all LEDs be “OFF”, and thus any ambiguous display is
avoided. Various novel displays are possible.
Much of the display flexibility derives from the fact that all outputs are individual, DC
regulated currents. Various effects can be achieved by modulating these currents. The individual
outputs can drive a transistor as well as a LED at the same time, so controller functions including
“staging” control can be performed. The LM3914 can also act as a programmer, or sequencer.
The LM3914 is rated for operation from 0°C to +70°C. The LM3914N-1 is available in an
18-lead PDIP (NFK) package.
The following typical application illustrates adjusting of the reference to a desired
value, and proper grounding for accurate operation, and avoiding oscillations.
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