Gold doped silicon compandor diodes for N2 and N3 carrier systems

Companding has proven to be a valuable technique for improving the signal-to-noise ratio of voice transmission at baseband frequencies. A compandor consists of a compressor element which reduces the dynamic range of a transmitted signal in a predetermined manner and an expandor element which restores the signal range at the receiver. Practical Bell System applications to date have used electron tubes, germanium point-contact semiconductor diodes and unpassivated silicon mesa diodes. Each of these variolosser elements had serious shortcomings. Two new diode pairs have been designed which eliminate the problems of impedance range control and linearity, diode noise and electrical stability. The new design utilizes heavy gold doping of a planar oxide-passivated wafer design to produce a bulk controlled device capable of unusually high manufacturing yields.