A new bidirectional solid-state switch for telephone loop plant applications

A new high-power bidirectional solid-state switch is described which uses a buried gate layer to pinch the electron hole plasma of a lateral p-i-n diode against the top oxide of a planar structure to produce bilateral blocking. Models of the switch have so far demonstrated blocking voltages up to 500 V, current break capability at currents up to 5 A and "on" state resistance of 1-4 Ω. Millisecond simulated lightning induced surges of up to 17 A have been passed through the switches without damage. The switch is designed for application primarily in telephone loops, where it can be used to control ringing signals, provide test access and perform signaling functions. Circuits are shown demonstrating how the switch may be used as an electrically coupled switch, an optically coupled relay for switching ac or dc, a transient immune crowbar voltage clamp and a short duration line interrupt switch for loop testing.