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Threshold Device

IP.com Disclosure Number: IPCOM000096170D
Original Publication Date: 1963-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 41K

Publishing Venue

IBM

Related People

Buelow, FK: AUTHOR [+2]

Abstract

The threshold device represents a combination of a plurality of feedback current switches 20, 40, 60. Each comprises two transistors 21 and 22, 41 and 42, 61 and 62, respectively. The device produces in binary form a sum output S and a carry output C in response to respective input current levels L0, L1, L2, L3 (Note table).

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Threshold Device

The threshold device represents a combination of a plurality of feedback current switches 20, 40, 60. Each comprises two transistors 21 and 22, 41 and 42, 61 and 62, respectively. The device produces in binary form a sum output S and a carry output C in response to respective input current levels L0, L1, L2, L3 (Note table).

By suitably chosen values of the emitter resistors (R20>R40>R60), the bias voltages from supply 11 in connection with the input signal levels appearing at bases 26, 46, and 66 have the following relationship with respect to the emitter potentials of respective transistors 22, 42, and 62.

With input current level L0 (case 1), the voltages appearing at bases 26, 46, 66 are, for transistors 22, 42, 62, above the respective emitter potentials. Therefore, all 22, 42, 62 are conducting. This causes their collector potentials to assume a potential which, dependent on the value of emitter resistors, becomes close to the negative voltage of supply 13. Thus, transistors 21, 41, and 61 are non-conducting. With input current level L1 (case 2) which is more negative than level L0, a voltage drop occurs across resistor 12 reducing the potential of bases 26, 46, 66. The base potential goes below the potential of emitter 24 but still remains above the potential of emitters 44 and 64. Thus, transistor 22 is cut-off whereas transistors 42 and 62 conduct. With input current level L2 (case 3), the base potential goes below the potential of emitters 24 and 44 but still remains above the potential of emitter 64. Transistors 22 and 42 are cut-off. Transistor 62 still conducts. With input current level L3 (case 3), the voltages at the bases are, for transistors 22, 42, 62, below the respective emitter potentials. Thus, these transistors are non-conducting.

In case 1, the sum output S = 0 is a predetermined amount of current in the sum circuit dependent on supply 14, voltage divider 15, the conductive state of transistor 42 and the non-conducti...