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Emitter Coupled Logic Circuit Using Complete Vertical Balancing

IP.com Disclosure Number: IPCOM000083378D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Rabbat, NB: AUTHOR

Abstract

The capacitance Ccus of the current source Q1 is an indirect cause of feedthrough. When X1 is low and held constant and X2 is making a transition from low to high or vice versa, the transition due to X2 is coupled to Vj and to the base of Q6 and hence to the output. This is the case without the introduction of Q'4. If Q1 was an ideal device the transition of X2 would have not been coupled to Q6, which would have remained low if X1 was low. The introduction of Q'1 avoids that problem.

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Emitter Coupled Logic Circuit Using Complete Vertical Balancing

The capacitance Ccus of the current source Q1 is an indirect cause of feedthrough. When X1 is low and held constant and X2 is making a transition from low to high or vice versa, the transition due to X2 is coupled to Vj and to the base of Q6 and hence to the output. This is the case without the introduction of Q'4. If Q1 was an ideal device the transition of X2 would have not been coupled to Q6, which would have remained low if X1 was low. The introduction of Q'1 avoids that problem.

Feedthrough due to Cit is as follows: When X1 is low, leakage currents charge Cit. A transition of X1 to high causes Q3 to provide the current to Q1, which is usually provided by Q2 and Rc1, until Cit is discharged. When Vi increases due to the charges of Cit, Vk also increases due to the leakage currents through Di charging Cid when X2 is low. The increase in Vk makes the base-emitter junction forward biased. Therefore, the transition of X1 from low to high finds appropriate conditions and Q3 turns on. The voltage Vi and Vj must remain constant, and the leakage currents must find an outlet other than Cit to prevent the increase of Vi. The introduction of Q'4 and Q'1 is for that purpose.

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