| 摘要 |
A vertical type surge protection device for absorbing surges of either polarity has a second region forming a first pn junction with a first region, a third region forming a first minority carrier injection junction with respect to the second region, a fourth region forming a second pn junction with the first region and a fifth region forming a second minority carrier injection junction with the fourth region. When the absolute value of a surge voltage applied across the device exceeds the breakdown voltage, either the one of the first and second pn junctions that is reverse biased owing to the surge polarity breaks down or punch-through occurs between the first and third regions or between the first and fifth regions, whereafter breakover ensues as a result of positive feedback. For preventing breakover from being caused by noise having a dV/dt value not greater than a prescribed value, the short-side direction length of the third and fifth regions, in the case they are rectangular, or the diameter thereof, in the case they are circular, is determined on the basis of the prescribed dV/dt value.
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