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Noise-Tolerant Sense Amplifier

IP.com Disclosure Number: IPCOM000041606D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Huffman, DR: AUTHOR [+2]

Abstract

High voltage (VH) is supplied to the semiconductor devices of a bucket brigade sense amplifier through an improved switching circuit which is effective during the standby interval, while the bit lines are in a balanced charge state, to keep the sense nodes of the amplifier isolated from noise fluctuations in the VH supply without thereby rendering these nodes susceptible to voltage imbalances that otherwise might be caused by extraneous disturbances, such as alpha particle radiation. This is accomplished by keeping the sense nodes coupled to the high voltage supply terminals of the amplifier during standby, while these terminals are isolated from the noise-prone VH supply by turning off the switching circuit.

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Noise-Tolerant Sense Amplifier

High voltage (VH) is supplied to the semiconductor devices of a bucket brigade sense amplifier through an improved switching circuit which is effective during the standby interval, while the bit lines are in a balanced charge state, to keep the sense nodes of the amplifier isolated from noise fluctuations in the VH supply without thereby rendering these nodes susceptible to voltage imbalances that otherwise might be caused by extraneous disturbances, such as alpha particle radiation. This is accomplished by keeping the sense nodes coupled to the high voltage supply terminals of the amplifier during standby, while these terminals are isolated from the noise-prone VH supply by turning off the switching circuit. During standby, the VH voltage is sufficiently low to inhibit the flow of sub- threshold currents through the bucket devices of the sense amplifier. Fig. 1 shows switching circuitry for coupling the VH supply to each of the VHS terminals of the sense amplifier shown in Fig. 2. The sense amplifier is of the bucket brigade type comprising devices 1 and 2 for coupling the VHS terminals respectively to the sense nodes N1 and N2, which are connected respectively to the drains of the cross-coupled bucket devices 3 and 4. The left and right lines of the differential bit lines are connected respectively to the sources of the bucket devices 3 and 4. The sense nodes N1 and N2 also are coupled through capacitors C1 and C2, respectively, to the drain boost (DB) voltage terminal. Prior to sensing the bit line signal, the amplifier is placed in a standby condition by raising the drain high restore (DHR) voltage at the gates of the devices 1 and 2, thereby turning on these devices and causing the left and right bit lines to become charged through the bucket devices 3 and 4 to the VH-VT level, where VT is the device threshold voltage. At this point the devices 3 and 4 turn off, leaving the voltages at the sense nodes N1 and N2 in a balanced state. When the bit lines are to be sensed during readout, the standby interval is terminated by lowering the DHR voltage and raising the DB voltage. Depending upon the bit line voltages at the sources of devices 3 and 4 during readout, the sense node voltages are unbalanced one way or the other, and the resulting signal is amplified by the devices 3 and 4 to produce the amplified signal voltage across N1 and N2. If the drains of the devices 1 and 2 (Fig. 2) were connected directly to the VH supply, as is commonly done, then during the interval when the devices 1 and 2 are conductive, any noise originating in the VH supply would be transferred to the sense nodes N1 and N2. Previously, it has been the practice to minimize such noise transference by bringing DHR to a low level after the sense lines were charged during standby, thereby isolating the sense nodes to block out any VH noise. This has the disadvantage that complete isolation of the sense nodes from a voltage supply...