Browse Prior Art Database

Writing FET Memory Cells with Precharged Bit Line

IP.com Disclosure Number: IPCOM000084463D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Chu, WM: AUTHOR [+5]

Abstract

The drawing shows an N-channel 5-device field-effect transistor (FET) cell with its pair of diffused bit lines. (Bit line 1 and bit line 2). The diffused bit lines are shown as distributed RC models. Devices 3 and 4 are input/output (I/O) devices and 7 and 8 are bit switch devices. Together they perform matrix selection of cells in an array.

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Writing FET Memory Cells with Precharged Bit Line

The drawing shows an N-channel 5-device field-effect transistor (FET) cell with its pair of diffused bit lines. (Bit line 1 and bit line 2). The diffused bit lines are shown as distributed RC models. Devices 3 and 4 are input/output (I/O) devices and 7 and 8 are bit switch devices. Together they perform matrix selection of cells in an array.

During the restart period, node "WL". "BL", "WRITE" are down and node "R" is up. The bit lines, along with their associated stray capacitances, are precharged to some positive potential. During the write cycle, node R is down and nodes WRITE, WL, BL are up.

Depending on the information to be written, either DI or DI will also be up. Assume that DI is up, bit line 2 will discharge toward ground. Node 2 of the cell will also discharge through device 4 as device 2 is unable to hold node 1 up due to its high impedance. Meanwhile, node 1 will rise due to the discharge of bit line 1 through devices 3 and 5. The perturbation introduced will always switch the state of the cell, provided that the "on" impedance of devices 7 through 12 is much smaller than the impedance of the load devices 1 and 2.

After the cell switches its polarity, device 5 shuts off and the remaining charge on bit line 1 with this write a positive potential into node 1. The resultant voltage on node 1 with this write scheme is typically 3 to 4 volts for a +8.5 volt system. During read cycles node WRITE is down and...