SOLID-STATE CODERS

1,134,441. Analogue to digital converter. STANDARD TELEPHONES & CABLES Ltd. 13 Jan., 1967 [14 Jan., 1966], No. 1857/66. Heading G4H. [Also in Division H1] A semi-conductive circuit arrangement comprises a body exhibiting high field instability (e.g. Gunn) effects, having decreasing crosssection resistance from one end to the other, and which is biased by means including an input signal, to a level less than the instability threshold value, so that on the application of a trigger pulse, a high field domain is created which propagates along the body distance dependent on the level of the input signal; the. domain ceases where the lower resistance reduces the field below that necessary to sustain the domain As the domain propagates along the body a series of output pulses representative of the input signal are provided by means such as that shown in Fig. 6 comprising grooves 4 cut into the body 1, each reduced cross-section providing a current pulse as it is traversed by the domain. The reducing resistance is provided in Fig. 6 by making the body 1 wedge shaped. In an alternative arrangement, the periodic changes in resistance are provided by changes in doping instead of grooves; in a further embodiment (Fig. 8) the pulses are obtained from a sequence of electrodes 15 insulated from the body by a a silica layer 22. Instead of a wedge shape, the body may be shaped to provide a logarithmic or other law. The semi-conductor may consist of Ga As or InP and the electrodes of tin. The device may be used as a solid state coder to provide analogue to digital conversion.