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Bit Line Bias Circuit With High Noise Immunity

IP.com Disclosure Number: IPCOM000082981D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Askin, HO: AUTHOR [+4]

Abstract

A DC bias is required to operate static 4-device cell arrays. Introducing high-frequency noise spikes to the bit lines from the power supply or allowing low-frequency noise to exist on the bit lines, will cause a decrease in the bit line sense signal. Shown is a circuit that provides the needed DC bias, and can keep the bias constant, even when subjected to noise conditions.

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Bit Line Bias Circuit With High Noise Immunity

A DC bias is required to operate static 4-device cell arrays. Introducing high- frequency noise spikes to the bit lines from the power supply or allowing low- frequency noise to exist on the bit lines, will cause a decrease in the bit line sense signal. Shown is a circuit that provides the needed DC bias, and can keep the bias constant, even when subjected to noise conditions.

Current for the array is supplied through device T4. This current is distributed to the bit lines through bit line load devices TA and TB. Each pair of the bit lines have separate bit line load devices. The remainder of the circuit (devices T1 to T4) is used once on each chip. The VHH node is at a voltage level which is produced on the chip, and is at a voltage level that is greater than the VH voltage plus two threshold voltages.

Devices T1 and T2 are high-impedance devices that produce a voltage at node A which keeps device T3 in a linear state. Device T3 is also a high- impedance device.

Since no current is drawn from node B the node B voltage is approximately equal to the VH voltage. The size of device T4 is determined to give the desired voltage at node C (considering the current drawn by the array), to place the bit line load devices TA and TB in a linear state. Since devices TA and TB are linear, the resulting bit line voltages is determined by the voltage at node C.

If high-frequency noise spikes occur on the VH supply, device T4 (being...