I'm working on a circuit which measures the phase difference between to signals that work in ultrasound range (~20 kHz).
But now I need to use only positive DC.
The changes I made in the circuit allow me to detect positive phase difference (when I change the bottom generator) but it gives only ~0v when I put a negative value in the generator.
I want to bias the output so the circuit works as the old one but mounted to a DC. The range will be divided by two but it doesn't matter.
Here are the links to both circuits in LTSpice https://www.dropbox.com/sh/be6k6jhx6h9ipo5/AACywKL40KTgJz2wyFPXie0sa?dl=1