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The problem with your circuit



is that an N FET needs a voltage that is typically 8V higher than its drain. When the top N FETs are conducting, their drains are at +12V, so you would need ~ +20V to make them conduct well.

The solutions for this problem are:


use P FETs for the top ones (and change the circuit somewhat)
use a driver circuit that has a boost circuit that generates the higher voltage


Other problems with your circuit are the risk of shoot-through, and the driving capacity of the circuit that drives the gates (which you do not show).