Browse Prior Art Database

Light Controlled Read Only Storage

IP.com Disclosure Number: IPCOM000094163D
Original Publication Date: 1966-Jun-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Guydos, NM: AUTHOR [+2]

Abstract

This storage unit uses three diodes per bit of storage. Such arrangement reduces the number of address lines required in the array and facilitates manufacture by integrated circuit techniques.

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Light Controlled Read Only Storage

This storage unit uses three diodes per bit of storage. Such arrangement reduces the number of address lines required in the array and facilitates manufacture by integrated circuit techniques.

In the 2-D array shown schematically in A, each bit position is defined by three diodes 1, 2, and 3. Each diode 1 is connected to a selected X drive line. Each diode 2 is connected to a selected Y drive line. Each diode 3 is connected to a common current sense amplifier SA. Diodes 1 and 2 are photodiodes which, when both reverse biased in a particular bit position and exposed to light, provide photocurrent through the corresponding diode 3 to SA.

Drawing B shows this array implemented by integrated circuit techniques. The X and Y drive lines are connected to N material embedded in P material to define the respective diodes 1 and 2. Diodes 3 are defined by the junction of the P material with a common N substrate. The latter has a conductive strip 4 along its underside to provide substantially uniform impedances between each bit position and SA.

Drawing C shows the characteristics of the photodiodes 1 and 2 when exposed to light as compared to diodes 3, which are always masked off from light. Drawing D shows a lighted bit position, a logical 1, in the half-select state in which diode 1 is reverse biased, diode 2 is forward biased, and photocurrent Iph of diode 1 and the thermally generated leakage Is of diode 3 flowing through diode 2. The f...