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Current Switch Logic Circuit

IP.com Disclosure Number: IPCOM000074909D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Cole, TG: AUTHOR [+2]

Abstract

The use of PNP transistors to provide a defined source of current and NPN transistors to define a sink of current is well known. However, when PHP loads are used together with NPN current sinks, problems of tolerancing can cause excessive power dissipation.

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Current Switch Logic Circuit

The use of PNP transistors to provide a defined source of current and NPN transistors to define a sink of current is well known. However, when PHP loads are used together with NPN current sinks, problems of tolerancing can cause excessive power dissipation.

Fig. 1 shows a conventional double-emitter-coupled current switch logic circuit using a PNP current source as a load and an NPN current sink to define the tail current.

IL is chosen to given minimum rise time on the output node:

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