Miscellaneous active electrical nonlinear devices – circuits – and – Specific signal discriminating without subsequent control – By amplitude
Reexamination Certificate
1999-05-24
2001-06-26
Lam, Tuan T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific signal discriminating without subsequent control
By amplitude
C327S051000
Reexamination Certificate
active
06252429
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to silicon-on-insulator circuits in general, and in particular to a method and apparatus for improving silicon-on-insulator complementary metal-oxide-semiconductor circuits. Still more particularly, the present invention relates to a method and apparatus for improving device matching and switching point tolerance in silicon-on-insulator cross-coupled complementary metal-oxide-semiconductor circuits.
2. Description of the Prior Art
In recent years, the predominant processing technology for integrated circuits has been the bulk complementary metal-oxide-semiconductor (CMOS) technology using silicon as substrates. Although bulk CMOS technology offers various advantages, such as low power consumption and stability, over other types of processing technologies, there are also several drawbacks associated with CMOS circuits, such as relatively slow speed and potential latchup problem. In light of such, a new processing technology called Silicon-on-Insulator (SOI) technology has emerged. Instead of using an semiconductor substrate like the bulk CMOS technology, SOI utilizes an insulating substrate, which provides tremendous improvements in certain circuit characteristics, such as speed and latch-up, over bulk CMOS technology. A detailed description of SOI technology can be found in Weste and Eshraghian,
Principles of CMOS VLSI Design: A Systems Perspective
, 2nd ed., pp. 125-130, Addison Wesley (1995), the pertinent portion of which is incorporated herein by reference.
For SOI circuits having transistors in a dual-rail cross-coupled configuration, mismatch and lack of symmetry of transistors on each rail can be attributed to body potential or threshold voltage differentials in transistor characteristics. The body potential is dependent upon the operating history of a circuit. The mismatch and lack of symmetry is also a direct result of dissimilar time constants to discharge the bodies of the transistors compared to the actual circuit access or cycle times. This disclosure describes an apparatus for improving device matching and switching point tolerance in SOI cross-coupled circuits.
SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention, a silicon-on-insulator circuit includes first and second sets of transistors, first and second rails, and first and second discharge transistors. The first set of transistors is cross-coupled with the second set of transistors. The first rail is connected to each gate of the transistors in the first set, and the second rail is connected to each gate of the transistors in the second set. The body of at least one transistor within the first set of transistors is connected to the first discharge transistor having the same channel type as the connected transistor. The body of at least one transistor within the second set of transistors is connected to the second discharge transistor having the same channel type as the connected transistor. The gate of the first discharge transistor is controlled by the second rail, and the gate of the second discharge transistor is controlled by the first rail.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description.
REFERENCES:
patent: 6028455 (2000-02-01), Yamauchi
patent: 6031775 (2000-02-01), Chang et al.
patent: 6046609 (2000-04-01), Toyoshima et al.
Assaderaghi Fariborz
Chuang Ching-Te Kent
Kuang Jente Benedict
Bracewell & Patterson L.L.P.
International Business Machines - Corporation
Lam Tuan T.
McBurney Mark E.
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