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This circuit
uses just one IC and a very few number of external components. It
displays the audio level in terms of 10 LEDs. The input voltage
can vary from 12V to 20V, but suggested voltage is 12V.
The LM3915
is a monolithic integrated circuit that senses analog voltage
levels and drives ten LEDs providing a logarithmic 3 dB/step
analog display. LED current drive is regulated and programmable,
eliminating the need for current limiting resistors.
The IC
contains an adjustable voltage reference and an accurate ten-step
voltage divider. The high-impedance input buffer accepts signals
down to ground and up to within 1.5V of the positive supply.
Further, it needs no protection against inputs of ±35V. The input
buffer drives 10 individual comparators referenced to the
precision divider. Accuracy is typically better than 1 dB.
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