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Very Low Power Random Access Memory Cell

IP.com Disclosure Number: IPCOM000052001D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 3 page(s) / 78K

Publishing Venue

IBM

Related People

Simi, VM: AUTHOR

Abstract

A cross-coupled memory cell has enhancement-mode FETs of zero volt threshold and 1:1 width-to-length ratio connected gate-to-source as loads. Cell size and power dissipation are reduced, while stability to unregulated power sources and fast operation are achieved.

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Very Low Power Random Access Memory Cell

A cross-coupled memory cell has enhancement-mode FETs of zero volt threshold and 1:1 width-to-length ratio connected gate-to-source as loads. Cell size and power dissipation are reduced, while stability to unregulated power sources and fast operation are achieved.

Fig. 1 shows a single cell in a memory array of a multitude of such cells. The word line is driven to select a cell, while the bit lines are driven transferring data into and out of the selected cell.

When the word line and the bit line to Q5 are driven high, Q3 is turned on and Q4 is turned off. Q1 functions as a high-resistance load. This resulting state continues and represents a logical 1 or
0. The opposite logic is stored when Q4 is driven through the selection of Q6. The gate of Q3 is then grounded and Q2 acts as a load resistor.

Q1 and Q2 are enhancement-mode devices which have zero thresholds. This can be achieved by withholding ion implant or changing the dose, as appropriate, in the particular chip fabrication technology. Q3, Q4, Q5 and Q6 are conventional enhancement-mode FETs, with thresholds in the one volt range. The width-to-length (W/L) ratio of Q1, Q2, Q3 and Q4 is 1:1, while that of Q5 and Q6 is selected to provide cell stability during read operations.

The gate and source of Q1 are connected directly together, as are the gate and source of Q2. Fig. 2 shows the drain current of the devices for varying gate- to-source potentials. The substrate voltage (not shown) and implant dose are selected to provide a cell current of 10/-9/ amperes using W/L...