Led Millivoltmeter

  
This circuit uses a dc amplifier (324) in a bar-graph circuit that uses an LM339 Quad comparator IC to sense dc levels.
Led Millivoltmeter - schematic

The LEDs will light every 100 mV. The 324 op amp is configured to provide a gain of 100 to increase this sensitivity to 1 mV. Two auxiliary LEDs indicate "power on" and "xlOO" gain setting.




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