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THREE LEVELS of Cascode With Differential and Single-Ended Circuits Under 3.4 Volts

IP.com Disclosure Number: IPCOM000038877D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 59K

IBM

Related People

Beranger, H: AUTHOR [+5]

Abstract

With conventional ECL (emitter-coupled logic) single-ended circuits, it is possible to cascode only 2 levels in the same ECL tree. With the ECL differential three levels can be cascoded under the same 3.4-volt power supply. (Image Omitted) This article presents a new circuit which can uses a mix of the 2 types of ECL with three levels of cascode. The main advantage of such a circuit is to increase the number of logical functions which can be implemented in a single circuit (tree), resulting in an overall decrease of the power dissipation and in the number of devices. The proposed circuit has 3 levels of cascode ECL under 3.4 volts which is a standard power supply. The 2 upper levels can be used with single-ended or differential ECL circuits while on the lower level only differential ECL is possible.

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THREE LEVELS of Cascode With Differential and Single-Ended Circuits Under 3.4 Volts

With conventional ECL (emitter-coupled logic) single-ended circuits, it is possible to cascode only 2 levels in the same ECL tree. With the ECL differential three levels can be cascoded under the same 3.4-volt power supply.

(Image Omitted)

This article presents a new circuit which can uses a mix of the 2 types of ECL with three levels of cascode. The main advantage of such a circuit is to increase the number of logical functions which can be implemented in a single circuit (tree), resulting in an overall decrease of the power dissipation and in the number of devices. The proposed circuit has 3 levels of cascode ECL under 3.4 volts which is a standard power supply. The 2 upper levels can be used with single-ended or differential ECL circuits while on the lower level only differential ECL is possible. The following DC calculation shows that 3 levels of cascode are possible with differential but not with single-ended ECL circuits. With 10% of tolerance on the 3.4-volt power supply, the circuits have to operate with 3.06 volts. - THREE LEVELS DIFFERENTIAL: Vcc min = 3 Vbe + Vce + Vre

= 2.95 volts

Vre: is the voltage across the resistance in the

source of current and Vce across the transistor.

With Vbe = 0.85 V

Vce = 0.2 V

Vre = 0.2 V - THREE LEVELS SINGLE ENDED:

Vcc min = 2 Vbe + Vref3 + Vfsbd/2

Vref3 = Vbe + Vre + Vce (reference at bottom level)

Vcc min = 3.27 Volts

Vfsbd/2 = Half voltage swing of the DATA's with

Vref3 the lowest reference near the GND. With the mix of level, if the lowest level is differential, the calculation for 3 levels differential ECL can be applied. In this case the minimum power supply required is 2.95 volts which is compatible with the
3.4-volt power supply. The circuit in Fig. 1 ill...