/diy/ - Do It Yourself

>>2492373
If you just want to make a square wave, then you want a half-bridge, maybe an H-bridge. Look into driver ICs like the IR2184 (pic related), or for lower power ratings an integrated solution like the old L298N. Any motor driver chip will be able to output a square wave, and should be able to do so reasonably fast. The AD9833 outputting a square wave into the motor driver or half-bridge controller would do a reasonable job, though I don't see why you need to use an AD9833 as opposed to a simpler oscillator. It would be even simpler in some ways to just make a simple class-B amp with a few power BJTs, if you only need a few watts of output.
A resonant drive can give a lot more net power to the piezo (it's what they do for ultrasonic cleaners and cutters IIRC), but the frequency may drift a bit and it needs a more complicated driving circuit.

Just using a single transistor means you can sink current from the piezo, but nothing will actually pull current through it in the opposite direction.

No need to use a linear power amplifier for a square wave, you'll be slew-rate limited anyhow.