US Patent 7706112 Active clamp protection device

An active clamp device electrically couples first and second nodes in respective first and second supply domains referenced to ground potentials that can be different. The active clamp device comprises first and second active devices controlled by signals respectively referenced to the first and second supply domains that create a short-circuit or low impedance connection between the first and second nodes in normal operation and drive impedance between the first and second nodes high in response to a transient event.