Power semiconductors

If the current in a wire with a parasitic inductance of 10 nH changes by 10 A in 10 ns, approximately what voltage is induced?

  1. A1 V
  2. B10 V
  3. C100 V
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Answer: B. 10 V

The voltage across an inductance is V = L × di/dt: 10×10⁻⁹ H × (10 A ÷ 10×10⁻⁹ s) = 10 V. The faster the switching, the larger di/dt, so even a small parasitic inductance produces a large surge voltage.

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