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Threshold Circuits

IP.com Disclosure Number: IPCOM000096664D
Original Publication Date: 1963-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Akmenkalns, IG: AUTHOR

Abstract

Threshold logic circuits operate by comparing a signal representing some linear combination of the input signals to a normally fixed reference signal. This can be expressed mathematically as: (Image Omitted); A decision is made when either a >= 0 or a <= 0

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Threshold Circuits

Threshold logic circuits operate by comparing a signal representing some linear combination of the input signals to a normally fixed reference signal. This can be expressed mathematically as:

(Image Omitted)

A decision is made when either a >= 0 or a <= 0

Summing networks constructed from a large number of resistors have been impractical due to: (a) tolerances on input signals; (b) feedBACK effects by the detector device; (c) resistor tolerances.

The drawings show currectors used in threshold circuits. The V-I characteristics of a nonpolarized and a polarized currector are shown in A and B, respectively. Above a certain knee-voltage V(ck), the current I(ct) through the device is essentially constant. This results in a well-controlled current through the threshold detector as long as the input signal is greater than some minimum signal. Such is determined by the voltage variations across the detector and by the knee voltage.

Using the nonpolarized currector as shown in C, positive and negative signal weights are obtained. D and E illustrate circuits implementing the general function:

(Image Omitted)

Any current or voltage detector such as a transistor, can be used in circuitry of this type.

The threshold logic circuits shown, signal tolerance and detector loading effects on the performance are minimized. Furthermore, circuitry for obtaining positive and negative weights is indicated. Since devices with several current ratings are available, vari...