Bell Telephone Laboratories

Mahmoud A El Hamamsy

William C King

Adrian R Hartman

Orval George Lorimor

Gee-Kung Chang

Stephen Knight

An optically toggled bidirectional normally-on switch is provided with protection against bilateral voltage and bidirectional current surges by the inclusion of a pair of oppositely poled thyristors. One version uses a large junction-type field-effect transistor in its main path and a pair of smaller junction-type transistors in the subsidiary path. A photodiode array controls the gate voltage on each of the transistors and turns them off when illuminated. A control node in the subsidiary path is connected to the gates of the SCRs so that excess current in this path turns on the appropriately-poled thyristor to provide an additional shunt path for the current.

Optically toggled bidirectional switch

A normally OFF linear bilateral switch using two VMOS FETs is described. The conduction state of the two VMOS FETs is controlled by a photodiode array optically coupled to a light emitting diode. A break-before-make switch may be constructed using this switch together with a normally ON JFET.

Normally off bilateral switch

An all solid-state protector circuit utilizes the combination of four zener diodes (Z1, Z2, Z3, Z4), two resistors (R1, R2), two capacitors (C1, C2), and two gated diode type switches (GDSA, GDSB) and provides bilateral voltage surge protection.

Bidirectional solid-state protector circuitry using gated diode switches

An optically toggled bilateral field effect transistor switch having a low leakage current is described. A high impedance path and, therefore, a low leakage current, is provided by a photovoltaically controlled field effect transistor.

Optically toggled bilateral switch having low leakage current

A bilateral switch uses a single photodiode array connected to the gate electrode of a voltage controlled device such as a field effect transistor or an antiparallel connected gated diode switch pair and, through appropriate diodes, to the drain and source electrodes of the field effect transistor or to the anode and cathode of the gated diode switch to control the current through the voltage controlled device. The photodiode array is optically coupled to a light-emitting diode located in an electrical input circuit.

Optically triggered linear bilateral switch

A device is described using a gated diode switch with its current conduction state controlled by a photovoltaically controlled field effect transistor connected in series with the gated diode switch.

Growing community of inventors

Watchung, NJ, United States of America

Mahmoud A El Hamamsy