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Multiple Input Nand Small Signal Driver

IP.com Disclosure Number: IPCOM000037749D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Banker, DC: AUTHOR [+4]

Abstract

The current mode off chip driver (Fig. 1) performs the Nand logical function as it drives a terminated transmission line. For simplicity of explanation input B will be held at an up level (logical 1) and only A will be switched.

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Multiple Input Nand Small Signal Driver

The current mode off chip driver (Fig. 1) performs the Nand logical function as it drives a terminated transmission line. For simplicity of explanation input B will be held at an up level (logical 1) and only A will be switched.

With input A at a down level (logical 0) T1 is on pushing current down the line forcing node 'out' into an up level. Since T5 is relatively off, T4 is not conducting. Current supplied through T6,D3 and JE charges the diffusion capacitance of D3.

When input A is raised to an up level T1 turns off. T5 turns on, and current flows from the transmission line through T4 and T5 thus bringing node 'out' to a down level. However, transitionally D3 discharges and an additional impulse of current is pulled from the transmission line. This additional impulse of current guarantees a down going transition overdrive switching condition. (Should input signal to terminals A and B be reversed then the current impulse would be provided by D2.) During this time D1 becomes forward biased and conducting current, thus charging up its diffusion capacitance in preparation for the up going transition at the transmission line. When input A switches to a down level the rising transition seen at node 'out' is assisted by the capacitive discharge of D1. Jc and Je provide the positive and negative current sources to the circuit. Js provides the required bias to T6.

Disclosed anonymously.

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