Browse Prior Art Database

Differential Transmission Scheme

IP.com Disclosure Number: IPCOM000048358D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Lebesnerais, G: AUTHOR [+2]

Abstract

The purpose of this circuit is to provide a differential line driver with a differential loading different from the common mode loading. The differential loading can be equal to the characteristic impedance of the line, while the common mode loading is adjusted to the circuit requirements of the line drivers and receivers.

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Differential Transmission Scheme

The purpose of this circuit is to provide a differential line driver with a differential loading different from the common mode loading. The differential loading can be equal to the characteristic impedance of the line, while the common mode loading is adjusted to the circuit requirements of the line drivers and receivers.

Network 1 provides a voltage level VM which is adjusted to be adapted to the DC voltage and current requirements of the driver. This circuit has an impedance higher than the characteristic impedance of the line without impacting the line termination, since the middle point M is an AC ground point with respect to the differential signal. This permits good control and a limitation of the current supplied by the drivers when their common mode output voltage changes due to power supply tolerance changes in the base to emitter voltage VBE of the transistors.

The reference generator is located close to the receiver circuit in order to minimize the common mode noise induced into M with respect to the receiver inputs.

With this arrangement, a better optimization of the driver and receiver circuits is obtained, especially with regard to power dissipation, when the driver circuit has a low output impedance.

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