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Cascode ECL Circuit With AC Coupled Push-Pull in Bicmos

IP.com Disclosure Number: IPCOM000120058D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Boudon, G: AUTHOR

Abstract

Disclosed is an active pull-down technique to improve the power-delay performance and the loading sensitivity of an ECL circuit. The ECL circuit is of the AC coupled type and can be used either in differential cascode ECL circuits or, as shown in the drawing, applied to a single-ended ECL circuit with reference voltages. Its efficiency is maximum in the latter case.

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Cascode ECL Circuit With AC Coupled Push-Pull in Bicmos

      Disclosed is an active pull-down technique to improve the
power-delay performance and the loading sensitivity of an ECL
circuit. The ECL circuit is of the AC coupled type and can be used
either in differential cascode ECL circuits or, as shown in the
drawing, applied to a single-ended ECL circuit with reference
voltages. Its efficiency is maximum in the latter case.

      The circuit shown in the drawing is more specifically a XOR2
cascode circuit, where the output buffer is made by a pair of NPNs,
TU1 and T1. The present disclosure mainly relates to the control
circuit of the bottom NPN, T1.

      An up-going transition is easy to obtain on the output of the
complete logic circuit, as it is performed by the emitter follower
NPN, TU1.

      The down-going is controlled by T1 which is in a DC state such
that a small DC current Io flows through it. This is made possible by
the reference current mirror circuit REF1 which comprises T3, T4, R3
and R4. The reference voltage is two Vbe's above ground and the
current defined in R4 is almost equal to the emitter current of T4.
The currents in R3 and R1 are also identical, resulting in a current
Io equal to the emitter current of T4. To save power, the resistances
R3 and R1 must have a high value. This can be done with small NFETs
having their gates connected to the reference voltage.

      When an up-going transition appears on output - (out-of-pha...