The following circuit should work for your purpose:
From left to right, we have a 25Hz square wave source. The actual frequency doesn't really matter, but what matters is that it is a 10V source, to fully turn the MOSFET on. Anything lower and you will start limiting current, so the voltage across your load will decrease (V = IR for Ohmic devices). Next, we see two 5V voltage sources in series with a center ground. If you probe (relative to ground) either of the other two terminals, you will see either +5V or -5V. Next, the +5V terminal is connected to the drain of an N-channel MOSFET. The -5V terminal is connected to the drain of a P-channel MOSFET, and the sources are tied together (I believe CMOS style?). The output of the source is shown in the scope window at the bottom. The yellow line (actually showing current) is zero, so it swings from +5V to -5V at 25Hz.
If you use this, make sure you understand MOSFET activation regions well enough to drive them at the correct voltage for their intended use. Also make sure to connect the load to the common source on the MOSFETs and to ground, not to the -5V terminal. Ground is a center "tap" (not actually, since it isn't a transformer coil), so be sure to use that as 0V/Gnd for any loads connected to this circuit. It's also worth mentioning that using a CMOS setup means you don't need to use an inverter, or even separate inputs to the MOSFETS. You only need to make sure your driving circuit runs a high enough voltage, and can provide enough current to overcome gate capacitance on two MOSFETs.
I hope that helps!