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Circuit Concept for Readily Reading and Writing Semiconductor Storages with Diode Coupled Cells

IP.com Disclosure Number: IPCOM000050479D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 74K

Publishing Venue

IBM

Related People

Wernicke, FC: AUTHOR

Abstract

The proposed select scheme and read/write circuit are suitable for storages, whose cells are coupled to the appertaining bit lines by diodes. Schottky-coupled cells are used to describe the inventive concept. SELECT AND READ

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Circuit Concept for Readily Reading and Writing Semiconductor Storages with Diode Coupled Cells

The proposed select scheme and read/write circuit are suitable for storages, whose cells are coupled to the appertaining bit lines by diodes. Schottky-coupled cells are used to describe the inventive concept. SELECT AND READ

Each cell is connected to an upper word line UWL and to a lower word line LWL (Fig. 1). For an unselected word line pair, transistor TW, whose collector is connected to the lower word line LWL, is switched off. The cells of the unselected word line are supplied with a very low standby current (approximately 10 microamperes per cell) by current source IST.

The n word line transistors TW have their emitters connected to a common current source IR, thus forming a multiple current switch. Each transistor TW is connected through its base to the output of a word decoder. When the word decoder is selected, a voltage V2 (approximately -2.5 V) is applied to its output, so that the appertaining transistor TW is ON. Assuming that the operations of the storage are not controlled by an external clock, one of the n word line transistors TW is always selected. Current IR (approximately 250 microamperes per cell) flows through transistor TW into the selected cells (Fig. 2). The great increase in the cell current (Iselect/ Istandby > 10) shifts the cell potential in a negative direction. Transistors TBLO and TBL1 Transistors TBLO and TBL1 of the sense amplifier keep the potential of the bit lines at the voltage value VBB, so that the potential at the cell node drops only until one of the two coupling diodes DO and D1 becomes conductive. In other words, current is drawn from the left or the right Schottky diode as a function of the stored information.

The current in the load resistors of the cell increases only by about 20 Microamperes, so that the greatest part of the relatively high selection current flows from the emitter of TBLO or TBL1. Thus, the selection current acts as a read current, generating between nodes S0 and S1 in the sense amplifier a difference signal which determines the output level through the read amplifier.

Thus, after cell selection, no additional read current is supplied through the bit lines, but the high selection current remains constant, generating also the read signal as soon as the cell has reached i...