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Tristable Transistor Circuit

IP.com Disclosure Number: IPCOM000093126D
Original Publication Date: 1967-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Taub, DM: AUTHOR [+4]

Abstract

This circuit distinguishes between 1 and 0 bipolar input pulses of the type shown in drawing B. Initially, transistors T1 and T2 are both conducting, diodes D3 and D4 are nonconducting, and tunnel diodes D1, D2, D5, and D6 are in their low voltage states. Assume now that a 1 input pulse is applied between the bases of transistors T3 and T4. The initial positive excursion of this bipolar pulse from zero potential causes D1 and D2 to switch to their high voltage state. This causes D3 to conduct and T1 to turn off.

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Tristable Transistor Circuit

This circuit distinguishes between 1 and 0 bipolar input pulses of the type shown in drawing B. Initially, transistors T1 and T2 are both conducting, diodes D3 and D4 are nonconducting, and tunnel diodes D1, D2, D5, and D6 are in their low voltage states. Assume now that a 1 input pulse is applied between the bases of transistors T3 and T4. The initial positive excursion of this bipolar pulse from zero potential causes D1 and D2 to switch to their high voltage state. This causes D3 to conduct and T1 to turn off.

The conduction of D3 reduces the forward current through D5 and D6. Thus the switching of transistor T2 to its nonconducting state is inhibited so that the subsequent negative excursion of the bipolar input pulse in the opposite direction does not switch T2 to its nonconducting state. If a 0 bipolar pulse had been applied to the bases of T3 and T4, T2 would have been switched to its nonconducting state and T1 would have been inhibited from switching.

Resetting of the circuit is accomplished by supplying sufficient current to the collectors of T3 and T4 to switch tunnel diodes D1, D2, D5, and D6 back to their low voltage state.

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