TABLE OF CONTENTS This goes back to my days at a well-known manufacturer of three-terminal, high-voltage switcher devices. To the uninitiated, these devices may look like a TO-220 Mosfet. But they are really quite remarkable, with an integrated 700V Fet and control, all on one die. One particularly nice thing about these devices is that the tab (of the TO-220 package) is at ground potential (connected to the Source terminal). So you can connect a heatsink to it without any insulation, and the heatsink won't end up spewing electric fields everywhere. The alternative is to use a controller IC driving an external Fet, for which you would need to insulate the tab of the Fet from the heatsink (the Mosfet tab is usually connected to the Drain, which is a swinging voltage node in a Flyback application). Then you would need to ground the heatsink to prevent it from becoming an antenna. Though it seems the part itself switches so fast, you do get a huge slew of EMI out of it anyway! Once in our 800W server power supply, the highest, most troublesome, and stubborn part of the EMI spectrum was actually discovered to be from the measly 25W standby power supply. This one was made from this particular monolithic integrated switcher!
However, it is still a nice device overall, and I would have thought you would never need to do the slightest "specmanship" to sell it. But ironically, I did learn much of...
