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Browse Prior Art Database

Self-Timing Fast Sense Amplifier

IP.com Disclosure Number: IPCOM000044354D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Tong, MH: AUTHOR

Abstract

In the present sense amplifier (Fig. 1) node XL is heavily loaded because it is tied to several devices. It is desirable to have node XL rise slowly so that enough signal can be developed across nodes SA and SA. Unfortunately, node XL continues to rise slowly after the sense amplifier starts sensing, making the sensing operation slow. Since node XL rises slowly, node N3 falls very slowly, causing loss in access time. A fast sensing circuit (Fig. 2) enables much faster sensing while the sense amplifier continues to be self-timing. Device T6 (Fig. 2) is relatively large compared to device T2 (Fig. 1). Device T2 can be made small to provide slow sensing initially without affecting the load on node XL. During standby, node N4 is precharged high by a precharge signal PC to clamp node N5 down to ground.

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Self-Timing Fast Sense Amplifier

In the present sense amplifier (Fig. 1) node XL is heavily loaded because it is tied to several devices. It is desirable to have node XL rise slowly so that enough signal can be developed across nodes SA and SA. Unfortunately, node XL continues to rise slowly after the sense amplifier starts sensing, making the sensing operation slow. Since node XL rises slowly, node N3 falls very slowly, causing loss in access time. A fast sensing circuit (Fig. 2) enables much faster sensing while the sense amplifier continues to be self-timing. Device T6 (Fig. 2) is relatively large compared to device T2 (Fig. 1). Device T2 can be made small to provide slow sensing initially without affecting the load on node XL. During standby, node N4 is precharged high by a precharge signal PC to clamp node N5 down to ground. During access, as node XL rises above a threshold voltage VT, node N4 is pulled down to ground fast, allowing node N5 to rise quickly, starting the fast sensing. This fast sensing circuit allows node XL rise time to be adjusted to start the slow sensing first phase (through device T2) with a relatively low signal across the SA. A fast sensing phase then follows, pulling SA (or SA) to ground fast, enabling the output to be activated. Since the SA sets quicker, input/output restore begins earlier. Devices T3, T4, T5, T3L, T4L and T5L can, therefore, be made smaller, saving some DC power.

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