GB1407152A - Semiconductor storage devic3 - Google Patents

Abstract

1407152 Integrated circuits NIPPON GAKKI SEIZO KK 31 July 1972 [31 July 1971 (2) 1 Sept 1971 22 Nov 1971 (3)] Divided out of 1406691 Heading H1K [Also in Division H3] The storage medium of an integrated semiconductor analogue store consists of a diffused resistive track with a plurality of tapping points, representing analogue values, which are selectively connected to an output terminal via switches operated in response to signals from read-out circuitry. The switches may be bipolar transistors or JUGFETs but as described are IGFETs the drains of which are constituted by side branches from the track and the sources of which are interconnected by a diffused strip. The gates may be connected to the terminals of read-out circuitry via a matrix of diffused tracks and deposited aluminium strips interconnected at selected intersections in accordance with fixed information to be stored. A suitable MOS circuit producing read out pulses at its terminals in a predetermined order in response to a train of clock pulses is described. Alternatively the store can be used as a function generator, e.g. to reproduce complex musical notes, or as a digital to analogue converter by connecting the gates to terminals of read-out circuitry at which pulses are produced in a sequence determined by coded digital input information. The resistive track may be of linear or zig-zag form with the tappings uniformly spaced along it. Alternatively in the zig-zag form the distance between tapings may progressively increase. To store logarithmically related quantities the track may be modified to form a distributed constant ladder-like attenuator network either by provision of branches, opposite those constituting the IGFET drains, the outer ends of which branches are grounded, or by providing along the edge of the track opposite the drains a metallic grounding strip or a series of interconnected grounded contacts. The structure including the matrix when present, is formed by conventional diffusion, oxide patterning and aluminium deposition techniques. Connections at selected intersections in the matrix are produced either by aperturing the oxide only at the selected points and depositing the aluminium strips to overlie the apertures or by providing apertures adjacent but offset from all intersections and providing the strips with side branches extending to selected apertures, the remaining apertures being optionally covered with isolated patches of aluminium for passivation.