Not so good with schematics =) Comparators are pretty simple. A common comparator will have power supply lines, VCC and GND and three other pins. input, output, and reference. When the signal going to the input is above the reference voltage the output is high, when it's bellow the reference the output is low, that's it. The easiest way to do this would be to use an equal resistor voltage divider from the MCU's power supply lines, basically setting the refrence at half supply for the MCU. But using VCC from the supply that drives the FET, the comparator is going to have better drive characteristics than a single transistor driver.