Problem with motor drive IGBTs

[MotorLab]

Hi,

I was wondering if anyone knows the details of measruing the capacitance of an insulated gate bipolar transistor (IGBT). Specifically, the circuit shown in Figure 23c of

http://www.irf.com/technical-info/appnotes/an-983.pdf

shows a 1:10 transformer. Does anyone know what the transformer is for? Also, there are two ground connections which appear to be different. Any clarification on this would be appreciated very much.

 

[Lewish]

I never found it to be an issue. Most datasheets provide all the information you really need to know to design the driver circuit.
As to the ground in question, I suspect that is a typo. Not uncommon in app. notes and datasheets.