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Bi-Cmos Xor3/Xor-Not3 Circuits With Pass Transistors

IP.com Disclosure Number: IPCOM000036034D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Boudon, G: AUTHOR [+2]

Abstract

In Bi-CMOS technology, complex logic functions are built from basic traditionnal NAND and NOR Bi-CMOS circuits. To build an XOR 3 ways, widely used in full adders and multipliers, 7 Nand 2 ways are necessary. The proposed custom XOR/XOR-NOT 3 ways, based on pass transistors, are built with a reduced number of transistors and a reduced silicon area to perform the same logic function (Figs. 1 and 2).

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Bi-Cmos Xor3/Xor-Not3 Circuits With Pass Transistors

In Bi-CMOS technology, complex logic functions are built from basic traditionnal NAND and NOR Bi-CMOS circuits. To build an XOR 3 ways, widely used in full adders and multipliers, 7 Nand 2 ways are necessary. The proposed custom XOR/XOR-NOT 3 ways, based on pass transistors, are built with a reduced number of transistors and a reduced silicon area to perform the same logic function (Figs. 1 and 2).

The present proposal shown in Fig. 1 is based on the use of pass transistors in conventionnal CMOS logic followed by a Bi-CMOS inverter using NPN transistors for the driving capability.

Due to the use of pass transistors (transfer gates), the Bi-CMOS circuit operates with a full power supply voltage swing. Devices P2, P3, N2 and N3 provide the XOR function between In1 and In2 on node

(Image Omitted)

A without level degradation. Generally, the functions built with pass transistors in CMOS have a high or down level degraded by -Vt/+Vt (e.g., XOR2,...) requiring a small FET device to eliminate the DC current consumption. Devices P5, P6, N5 and N6 provide the XOR-NOT function between In1 XOR In2 (node
A) and In3. On node B, we have the complementary signal of the function In1 XOR In2 XOR In3. This provides the output with the given function: In1 XOR In2 XOR In3 (XOR 3 ways of In1, In2, In3). The signal output between the bipolar transistors T1 and T2 is CMOS compatible because of the PFET (P8) and the NFET (NX).

A simila...