Working

Our reference is 5V. The 4 identical 1kΩ resistors split this voltage equally into:

• 1.25V
• 2.5V
• 3.75V
• 5V

So our references are:

• Ref1 = 3.75V
• Ref2 = 2.5V
• Ref3 = 1.25V

Each comparator checks Vin against the reference voltage:

• U1 outputs 1 if Vin < 3.75V
• U2 outputs 1 if Vin < 2.5V
• U3 outputs 1 if Vin < 1.25V

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Output Conditions

U1	U2	U3	Vin Range	B1	B0
1	1	1	0 – 1.25V	0	0
1	1	0	1.25V – 2.5V	0	1
1	0	0	2.5V – 3.75V	1	0
0	0	0	3.75V – 5V	1	1