I was going through my old files and discovered some circuits I have built some time ago. Avery basic LED voltage level indicator using LM339 can be used to indicate 4 voltage levels between 0 and 4V.
The basic circuit is shown below. Each comparator is biased one step higher than the comparator below it. As the input voltage increases and exceeds the reference voltage on the comparator's inverting input, the output goes high and lights its respective LED. Output sink current for the LEDs is approximately 6mA. It can be extended to 8 levels with an additional LM339 comparator. The circuit was simulated with MultiSIM BLUE.
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