I am trying to build a circuit after a schematic but I am running into a cataclysmic problem with my circuit.. The mosfet symbol in the circuit drawing doesn't show a diode across Drain to Source yet the mosfet I picked and all of the mosfets I looked up online do. Is there a difference in this or is this just a difference in the circuit symbol but not the actual part?
the way most Mosfets are made automatically gives them something called a parasitic diode- that's what you are seeing in some schematic symbols for MOSFETS.
See page 30 of this link for a discussion on how the parasitic internal diodes sometimes get used for motor noise clamping:
So with a full-wave rectified (115vac line voltage) of ~60v with the positive at D and negative at S won't cause a direct short, correct? The mosfet I picked is rated 250v (Vds)
:o :oOk as soon as you mentioned 115VAC it started to sound like a bad, bad, bad idea. Do you have a schematic of what you are planning? Full wave rectified 115 will be 115 x 1.414 = about 155V. half-wave rectifed will be about half that. Anyway, post a schematic and let's see how dangerous this all really is...
Those H-bridge type circuits are for DC motors, not AC, in case that's your reference design.
-j
How do I post a schematic?
And no, I'm not trying to make an h-bridge.