Also a fun one. Made a discrete gate driver (20ns edge into rated load), runs nice and cool at 1MHz. Turn it up to 2MHz, starts warming up a little but still happy. 3MHz, running fairly hot. 3.4MHz, running really hot.
3.5MHz for a few seconds... the waveform slowly starts to kind of collapse as the transistors stop turning off. ;-)Tim
two MOSFETS in parallel?
If you are driving MosFets that have a higher potential at the drain than what the device at the gate can handle, the Cgd can be a real killer of gate driving devices.
Some people forget about that like I did not to long ago when switching a 400+ V load with a 10 Volt driving device. The 10ns pulse retreating back from the drain to the gate over time would kill the upper driver transistor. The transistor would just lose its gain but not actually get diode damaged.
This didn't happen all the time because of what was taking place on the load. I fix that problem with a zener.
I was looking at a Mosfet/bipolar totem type hybrid method for a gate driver. Because we still have some high power switching applications on the horizon.
Jamie
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