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Why does the body diode's recovery matter in a bridge circuit?

  • A.It prevents the freewheeling current from flowing at all
  • B.It raises the on-resistance of the conducting channel
  • C.It shifts the threshold voltage of the opposite device
  • D.Its stored charge causes a current spike in the opposite device

Answer: D

When the opposite device turns on, the body diode's stored charge must be swept out, and that appears as a spike of current through both devices at once - a real dissipation, and a source of switching noise as well. The diode carries the freewheeling current perfectly well rather than preventing it, and it affects neither the channel resistance nor the threshold. Reverse recovery in a parasitic that cannot be removed is one reason synchronous converters need careful dead-time control, and it is why some designs add a faster external diode in parallel.

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