4 Pin MOSFET, or Am I Just Confused?

[circuitb0y]

I'm new to all of this and I'm looking at a schematic that has me totally stumped. There's a component labeled "Q1" and it says "RF 511".
I know there's an IRF511 MOSFET, but from what I've seen, those are always 3 pins.
The component on my board looks like it has 4 pins, so I'm completely lost.

Am I misunderstanding the schematic, or is this actually a different component, like an IGBT? Any help would be awesome!

 

[mich4el.crx]

I could understand your confusion. You're likely looking at a standard 3-pin MOSFET, and that fourth pin you're seeing on the board is actually a drain tab or a heatsink connection. The metal drain tab on many MOSFETs is electrically connected to the drain pin. Sometimes schematics will show this as a separate connection for clarity, but it's not a fourth, independent pin. This is super common in TO-220 packages like the IRF511. So the schematic is just showing you how the component is laid out, including that metal tab. You've got the right part in mind with the IRF511. Hope that helps clear things up!

 

[sam.in.a.box]

I'm new to all of this and I'm looking at a schematic that has me totally stumped. There's a component labeled "Q1" and it says "RF 511".
I know there's an IRF511 MOSFET, but from what I've seen, those are always 3 pins.
The component on my board looks like it has 4 pins, so I'm completely lost.

Am I misunderstanding the schematic, or is this actually a different component, like an IGBT? Any help would be awesome!

It could be a custom or older package. IRF511 is definitely a 3 pin MOSFET, so if yours has 4 pins, it might be an IGBT or a MOSFET with a tab or pad counted as a pin. Confirm the board markings or trace connections sometimes schematics simplify pin counts