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Feedback Controlled AC-coupled Active Pull Down ECL/DCS Circuits

IP.com Disclosure Number: IPCOM000109705D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Anderson, CJ: AUTHOR [+3]

Abstract

Disclosed is a feedback-controlled ac-coupled active pull down scheme for ECL/DCS circuits which minimizes the loading to the logic stage and provides a sharp, self-terminating dynamic pull-down current.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 66% of the total text.

Feedback Controlled AC-coupled Active Pull Down ECL/DCS Circuits

       Disclosed is a feedback-controlled ac-coupled active pull
down scheme for ECL/DCS circuits which minimizes the loading to the
logic stage and provides a sharp, self-terminating dynamic pull-down
current.

      Recently, various active pull down schemes have been pursued to
reduce the power consumption and improve the pull-down delay of the
emitter-follower stage in high-speed ECL/DCS circuits.  One example
is the ac-coupled active pull down ECL circuit shown in Fig. 1 (1)
where a capacitor is used to couple a transient signal from the
in-phase collector-node of the current switch to the base of the
pull-down transistor.  In this configuration, however, the coupling
capacitor C sub X represents a load to the (critical) collector node
and hence large dynamic pull-down current (large coupling capacitor)
and fast switching of the logic stage can not be achieved
simultaneously.  Furthermore, this scheme requires two input signals
for the emitter-follower stage (one from the out of phase collector
node to the base of the emitter-follower transistor and the other
from the in-phase collector node to the base of the pull-down
transistor through CX), thus complicating the wiring, especially for
DCS implementation where both phases are needed.

      The disclosed scheme (Fig. 2 for ECL implementation) utilizes a
feedback capacitor to couple the transient signal from the collector
node of the emit...