Power semiconductors

In packages for fast-switching power devices, what is the purpose of a dedicated source terminal for the gate-drive return (Kelvin source)?

  1. ATo double the source current
  2. BTo keep the voltage across the inductance of the main-current source path from affecting the gate drive
  3. CTo make the package smaller
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Answer: B. To keep the voltage across the inductance of the main-current source path from affecting the gate drive

The source path carrying the main current has inductance, and rapid current changes produce a voltage across it. If the gate-drive return shares this path, the voltage opposes the gate voltage, slowing switching or causing oscillation. A Kelvin source is a terminal dedicated to the drive circuit that removes this effect.

  • A. It is not a terminal for increasing current.
  • B. Correct. It removes the effect of common source inductance.
  • C. It is not intended to shrink the package.
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