Browse Prior Art Database

Switchable Current Source Line Driver

IP.com Disclosure Number: IPCOM000077788D
Original Publication Date: 1972-Sep-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Couch, WD: AUTHOR [+2]

Abstract

The diagram shows a line driver circuit which can drive with substantial immunity from noise, a transmission line comprising long distances of twisted pair cable. It maintains a fixed output impedance which can be initially set to match the characteristic impedance of the transmission line.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 66% of the total text.

Page 1 of 2

Switchable Current Source Line Driver

The diagram shows a line driver circuit which can drive with substantial immunity from noise, a transmission line comprising long distances of twisted pair cable. It maintains a fixed output impedance which can be initially set to match the characteristic impedance of the transmission line.

A transmission line 1, which may be up to three miles of common twisted pair telephone type wires, is terminated in a receiver 2 at its far end. At the transmitter end, the line is bridged with its characteristic impedance which may be comprised of two resistors 4 and 5 in series across the line. The junction of the two resistors 4 and 5 is connected to one side of the power supply. The other end of each resistor 4 or 5 is connected to the collector of a transistor 7 or 8, respectively. Each transistor 7 or 8 has its base and emitter connected to the other side of the power supply through a resistor 9 and 10, respectively. The base of transistor 7 is also coupled through a resistor 11 to a terminal 12 which receives an input data signal, and similarly the base of transistor 8 is connected through resistor 13 to a terminal 14 receiving the complemental data signal.

The utilization of transistors 7 and 8, with their bias resistors 9 and 10 as current source drivers, allows the transmission line 1 to see only the resistors 4 and 5 as the terminating line impedance, since the high-impedance output of the current source drivers does not constit...