A two-terminal ABD with a voltage-current avalanche breakdown characteristic in both directions, which can be either symmetrical or asymmetrical.
NOTE Large transient currents will be clamped for voltage of either polarity across two similar p-n junctions in series connected in opposite directions. During a transient current event in this operating mode, one of the two p-n junctions is always in avalanche breakdown and the other is in the forward-conducting, low-voltage mode. The voltage across the bidirectional ABD is the sum of these two voltages. The avalanche breakdown voltage is substantially the same in both directions for a symmetrical bidirectional ABD; however, it may also be intentionally different or asymmetrical by design for special applications. Since multiple p-n junction capacitances in series reduce the overall total capacitance, the bidirectional ABD has lower capacitance than its unidirectional counterpart.
Bidirectional ABD symbol options