Browse Prior Art Database

Trigger

IP.com Disclosure Number: IPCOM000093059D
Original Publication Date: 1967-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Harper, LR: AUTHOR

Abstract

The circuit shows a latch coupled to a trigger which functions to store the previous setting of the latch. The latch comprises a pair of cross-coupled double emitter transistors 10 and 12 and a pair of gating transistors 14 and 16. The trigger portion of the circuit comprises transistors 18, 20, 22, and 24.

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Trigger

The circuit shows a latch coupled to a trigger which functions to store the previous setting of the latch. The latch comprises a pair of cross-coupled double emitter transistors 10 and 12 and a pair of gating transistors 14 and 16. The trigger portion of the circuit comprises transistors 18, 20, 22, and 24.

To set the latch, a downlevel signal is applied to terminal 26 and an uplevel signal is applied to the appropriate gate terminal 28 or 30. Assuming that the gate signal is applied to terminal 28, this causes transistor 14 to conduct. Thus the base of transistor 12 is lowered so that it goes out of conduction causing the base of transistor 10 to rise and causing transistor 10 to conduct.

To read out the setting of the latch, an uplevel signal is applied to terminal 26 which disables switching transistors 14 and 16 if the gating signal is not lowered. This signal also shifts the current in transistor 10 from the right-hand emitter to the left-hand emitter through transistor 18 which causes transistor 18 to conduct. The drop in the collector voltage of transistor 18 is coupled to the base of transistor 20, causing it to turn off. This action, in turn, causes transistor 24 to turn off. The rise in the collector voltage of transistor 24 is coupled to the base of transistor 22 to turn this on. This action reinforces the uplevel of the base of transistor 18.

Thus the loop is completed to keep transistor 18 in conduction until the setting of the latch is chang...