Electronic – Measure the Phase Difference

digital-logicvoltage

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This problem was asked in a paper recently. They have not clearly mentioned the circuit. Assuming a low pass circuit, I tried to draw some waveforms. And I can't think of any other circuit that they are expecting. They gave option (A) as the official answer but I can't understand how they are getting it. Please help me with this.

Best Answer

The problem doesn't mention any LP filter or any way the average voltage is actually generated (as you noted).
It just asks what will be the average voltage (i.e. you don't have to assume any LP circuit; average voltage of a signal is defined even if there is no circuit actually generating the average voltage).
In other words: What will be the duty cycle of the output of the XOR gate? Multiply that by \$V\$ and you get the average voltage.