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Dynamic Logic Circuit of Reduced Size

IP.com Disclosure Number: IPCOM000080272D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Halada, JR: AUTHOR [+6]

Abstract

By taking advantage of knowledge that logical inputs A, B, and C are mutually exclusive, and by returning padding capacitor 43 to +V rather than ground, substantial chip area can be saved. Without mutually exclusive logic inputs, field-effect transistor (FET) devices 11 through 23 would have to be large enough to discharge all connected device capacitances, as well as all net capacitances 31 through 35. Since inputs A, B, and C are mutually exclusive, by way of example, devices 11, 13 and 23 need not be designed to discharge capacitances 33 and 35 and, therefore, can be smaller in size.

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Dynamic Logic Circuit of Reduced Size

By taking advantage of knowledge that logical inputs A, B, and C are mutually exclusive, and by returning padding capacitor 43 to +V rather than ground, substantial chip area can be saved. Without mutually exclusive logic inputs, field-effect transistor (FET) devices 11 through 23 would have to be large enough to discharge all connected device capacitances, as well as all net capacitances 31 through 35. Since inputs A, B, and C are mutually exclusive, by way of example, devices 11, 13 and 23 need not be designed to discharge capacitances 33 and 35 and, therefore, can be smaller in size.

Additional chip area can be saved whenever a net such as net 41, which is an extension of the drain diffusion of FET 25 and source diffusion of FET 29 must be capacitively padded. The known padding technique would involve bringing net 41 to a metalization layer via an oxide through-hole, and then building a thin oxide capacitor over a ground diffusion area. If instead, the thin oxide capacitor 43 is built directly under an existing +V metallization, the drain and source diffusion extension which constitutes net 41 becomes one plate of capacitor 43. The areas for an oxide through-hole and for a separate capacitor are thus saved.

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