SSTC FET drive xfrmr

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Original poster: "Sean Taylor by way of Terry Fritz <teslalist-at-qwest-dot-net>" <seantaylor-at-attbi-dot-com>

Hi all,
I'm trying to make a FET drive transformer, and so far I'm not too
successful.  Right now it's just 15 turns of 22 gauge zip cord on a ferrite
core.  The input and output waveforms can be seen at:
http://hot-streamer-dot-com/temp/fetdrv.bmp

The top trace is the input to the tranformer, the bottom trace is the GE
junction of my IGBT.  I know the capacitance changes with the CE bias, but
it was just for testing.  I also simulated the junction with a capacitor to
see if it would act the same, and it did.  Anyway, as you can see, the rise
time is horrible on the IGBT side of the transformer.  Is this just because
the coupling between the winding is too low, ie the two windings aren't
wound around each other first?  The drive is a TC4421, and I have a couple
bypass caps in series for DC blocking, cause right how it's only operating
SE, but eventually the driver will be a full bridge.  Thanks for any help!

Sean Taylor