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Non-linear Diode Logical Circuits

IP.com Disclosure Number: IPCOM000098581D
Original Publication Date: 1959-Apr-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 4 page(s) / 52K

Publishing Venue

IBM

Related People

Thomas, LH: AUTHOR

Abstract

In the drawing, the non-linear diodes are encircled to distinguish them from other diodes. The term non-linear diodes refers to germanium diodes, known either as PNPN or negative resistance or positive gap or Reeves diodes. The latter are described by Reeves and Cooke, at pp. 112 to 117 of Electrical Communication , June 1955. They have a non-linear voltage-current characteristic such that a firing voltage of about 14 v. is required to initiate a high conduction. Once this state is achieved, the voltage required to maintain such conduction at about 12 ma. drops to about 3.3 v. Other non-linear voltage-current characteristic devices, having predictable firing voltages, are employable. It is unessential that they be unidirectional devices such as diodes. For instance, certain neon glow lamps could be used.

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Non-linear Diode Logical Circuits

In the drawing, the non-linear diodes are encircled to distinguish them from other diodes. The term non-linear diodes refers to germanium diodes, known either as PNPN or negative resistance or positive gap or Reeves diodes. The latter are described by Reeves and Cooke, at pp. 112 to 117 of Electrical Communication , June 1955. They have a non-linear voltage-current characteristic such that a firing voltage of about 14 v. is required to initiate a high conduction. Once this state is achieved, the voltage required to maintain such conduction at about 12 ma. drops to about 3.3 v. Other non-linear voltage- current characteristic devices, having predictable firing voltages, are employable. It is unessential that they be unidirectional devices such as diodes. For instance, certain neon glow lamps could be used.

Each of the currents flowing as indicated by the arrows is constant in value, with the means for maintaining such values not shown. There is a constant 6 ma. flowing upward from the point 10 of input unit A. If no other path is provided for this 6 ma., such as by conduction of diode 1A, the lower diode of the adjacent clamp, connected to a -8 v. source supplies the 6 ma. flow. In the absence of any signals, the potential of input A' is, therefore, established at -8 v. Similarly, in the absence of conduction of either of the diodes 1A or 2A, the constant 12 ma. flowing toward point 14 is provided with a path through diode 16 to the switching voltage source VS1. The center node current I(c) is also constant, and in the absence of any other adequate conductive path, at least a portion of I(c) flows through the diode of the adjacent clamp circuit, which is connected to the -4 v. source. The constant 12 ma. and 6 ma. currents of the output unit are similarly handled by the circuits completed through diode 18 to the switching voltage source VS2 and by the clamping diode connected to ground.

When operating as an OR circuit (I(c) = constant 6 ma.), VS1 has a normal value of about -8 v., but when operative for switching, this rises to about +12 v. With +12 v. at VS1, a total of approximately 20 v. is potentially available across 1A. This is more than sufficient to initiate high conduction in 1A. Substantially the entire 12 ma. flowing to 13 is then passed through 1A. This provides a new source for the constant 6 ma. flowing away from 10, and the additional 6 ma. flows through the upper (grounded) diode of the clamp to change 10 to a clamped ground potential.

Since 1A is highly conductive, the point 14 achieves a potential value of 3.3
v. Because of the blocking effect of 16, 14 no longer sees the +12 v. from VS1.

Diode 2A is not triggered to a high state during the foregoing, even though the node is clamped to -4 v. through the lower diode of its clamp. As VS1 increases toward +12 v., the 14 v. triggering value for 1A (connected to -8 v. clamp) is achieved before the triggering voltage value for 2A (conne...