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Memory Cell Read Write Preamplifier

IP.com Disclosure Number: IPCOM000075736D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Blount, FT: AUTHOR [+4]

Abstract

The read-write preamplifier is used to sense current flowing through one of the outside emitters of the memory cell shown, and to write information into the cell by creating a differential voltage at the outside emitters. The circuit is to be used in large numbers in an integrated circuit memory system, and thus it is designed to lay out in a small area. Only those devices within the dashed lines are required for each preamplifier. D1-T1 and D2-T2 are each laid out as one device. The circuit is also designed with only positive voltage supplies.

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Memory Cell Read Write Preamplifier

The read-write preamplifier is used to sense current flowing through one of the outside emitters of the memory cell shown, and to write information into the cell by creating a differential voltage at the outside emitters. The circuit is to be used in large numbers in an integrated circuit memory system, and thus it is designed to lay out in a small area. Only those devices within the dashed lines are required for each preamplifier. D1-T1 and D2-T2 are each laid out as one device. The circuit is also designed with only positive voltage supplies.

The read operation is as follows. The preamplifier is selected and powered up by raising the voltages V at terminals A, B and G. T1 and T2 act as equal current sources with the current established by VA, R1 and R2. These currents pull down points C and D. The cell current then flows into C or D if the voltage at G is raised. Assume T6 is on. The current from T1 divides between T6 and D1- R3. The current from T2 flows entirely through D2-R4. As a result, a voltage difference is established between E and F.

To write either T3 or T4 is saturated; the other is cut off. Suppose T3 is saturated. This pulls down C, forcing the cell current to flow into T6. V REF is used to recover C and D after a read or write operation.

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