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TTL Logic Circuit

IP.com Disclosure Number: IPCOM000073415D
Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Eardley, DB: AUTHOR

Abstract

This circuit has a large "off-to-on" noise tolerance.

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TTL Logic Circuit

This circuit has a large "off-to-on" noise tolerance.

Transistors T1 and T2 are multiemitter transistors. The emitter-base diodes of T1 are used to perform the logical AND function. The collector-base junction of T2 is used to raise the switching threshold of the circuit by an amount equal to its forward voltage. Saturating transistor T3 provides an inverted output.

During a turnoff transition, charge stored in the collector-base junction of T2 allows T2 to conduct. T2 then provides a low impedance path by which the base charge is removed from T3. The low impedance path is from the base of T3 through T2 (collector-emitter) to the output of the driving circuit. Therefore, as in the TTL circuit, T3 has a small saturation time.

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