LF: 500kHz PA with IR2110 driver

["James Moritz" <james.moritz@btopenworld.com>]

Dear Rik, LF Group,

The IR2110 delivers only a little more gate drive than a TC4426/7. Recently
I have been uprating my 10W EER transverter to 100W - driving the Mosfet
gates is about 3.7 times more difficult at 500k compared to 137k :-) I find
that the limiting factor on switching speed seems to be circuit strays
rather than the gate driver itself. Trying to charge and discharge a Mosfet
gate with the equivalent of some nF of capacitance in something of the order
of 100ns isn't easy, and is quite sensitive to circuit layout, decoupling,
grounding and so on.

The voltage-switching type of class D seems to be a bit better at the higher
frequency, partly because the drain current in the Mosfets is low around the
switching point, which means somewhat slower switching transitions are OK.
Also the drain-source voltages are somewhat lower at a given supply voltage,
which lets you choose a lower voltage Mosfet with less gate capacitance.

Cheers, Jim Moritz
73 de M0BMU