Hi Erika,

does your design use discrete semiconductors, or are you designing a monolithic circuit?

In the first case, I would start at the output, and work my way backward to the input. You know the output voltage and the output current. Is your load really an old-fashioned light bulb? If so, its inductance is quite low, so switching off will not be accompanied by high voltage peaks; however, after switching on the cold light bulb the current might well be twice or thrice the nominal value during the first milliseconds. To remain on the safe side, I would choose MOSFETs with VDS >= 1.2 * supply voltage, and ID >= 4 * nominal current of the light bulb.

You can choose from a variety of architectures. Perhaps the simplest is: an n-channel MOSFET at the low side, and a p-channel MOSFET at the high side. If your supply voltage is greater than 20 V, you'll need a level shifter in order to drive the high side MOSFET. If you need further transistors depends on the input voltage and the impedance of the source of the input voltage.

Coming to think of it, why do you need a half-bridge at all? With a light bulb, there is no basic difference between powering it by DC or by AC, and for just switching it off or on, a single MOSFET would be enough.