Loved your MOSFET video, which really helped clarify them for me. I'm planning a processor upgrade for an old iMac G4 and using your worksheet to try to determine whether I'll need to add a heatsink to the various MOSFETs on the logic board, starting with the IRF7822. I found the datasheet and have been using that to plug in values into the worksheet.
For step 1: The IRF7822 is an IC. The gate is pin 4, drain is pins 5–8, and source is pins 1–3. You can see how it's hooked up on page 22 of the iMac's schematics.
For step 2: VGS is 1V and VDS is 30V. I think VCC is +12V, but I'm not 100% sure, since the +12V power rail goes through a LTC1735CS voltage regulator before hitting the IRF7822s at Q30, Q33, and Q35, and I'm having a hard time following the voltage through that VRM. VLOAD should be 1.3V, which I'll be setting VGER_VCORE to, since the PowerPC 7457 I'll be putting in operates at 1.3V.
For step 3: Max RDS is 6.5mΩ, according to the IRF7822's datasheet. But the actual RDS? I can't figure that out. Figure 3 doesn't have a VGS of 1V on the x-axis, and I'm not sure if ID is going to be 15A or some other value.
For step 4, I've got 3.125W.
How do I figure out the actual RDS? Am I getting the VCC and VLOAD values right?