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'Differential pair' is a pair of conductors with special characteristics, used for differential signaling.
Examples of the differential pair include:

★ twisted-pair cables, shielded and unshielded

★ microstrip and stripline differential pair routing techniques on printed circuit boards
Differential pairs are usually found on a printed circuit board, in cables (twisted-pair cables, ribbon cables), and in connectors.
Differential pair can be considered as a PCB implementation of a well-known twisted-pair cable. However, from the modern point of view, twisted-pair is nothing but particular implementation of a differential pair.
Differential pairs are generally used to:

★ Carry differential or semi-differential signals, such as

★
★ High-speed digital serial interfaces (e.g. LVDS, SATA, Hypertransport, Ethernet, etc.)

★
★ High quality and/or high frequency analog signals (e.g. video signals, professional audio signals, etc.)

★ Minimize cross-talk and electromagnetic interference, both noise emission and noise acceptance by the signal carried by differential pair

★ Achieve constant and/or known characteristic impedance, which is important in high-speed signal transmission, to use impedance matching techniques

Contents

Amplifiers

See also

Uses of Differential Pairs

Data rates of some interfaces implemented with differential pairs

Links

Amplifiers

Differential pair can also refer to the pair of transistors used as the input stage of a differential amplifier.

See also

★ Characteristic impedance

★ Impedance matching

★ Twisted pair

★ Low-voltage differential signaling (LVDS)

★ Printed circuit board

★ Transmission line

★ Crosstalk (electronics)

★ Electromagnetic interference

★ Signal integrity

★ Differential TTL

Uses of Differential Pairs

★ PCI Express

★ LVDS

★ SATA

★ Backplanes

★ DDR2 SDRAM

Data rates of some interfaces implemented with differential pairs

★ Serial ATA 1.25 Gbit/s

★ Hypertransport 1.6 Gbit/s

★ Infiniband 2.5 Gbit/s

★ PCI Express 2.5 Gbit/s

★ Serial ATA II 2.5 Gbit/s

★ XZUI 3.125 Gbit/s

★ PCI Express II 5.0 Gbit/s

★ 10 GbE 10 Gbit/s

Links

★ High-Speed Board Designs application note by Altera

★ Differential Pairs article by Cadence Design Systems

★ Interactive and Differential Pair Routing by Altium Limited

★ Designing with Differential Pairs in What’s New in Altium Designer 6, Altium

★ Demystifying PCB Impedance Control, Practical PCB Formulas and Plots - Jose Alvarellos, August 30, 2001

★ PCB Trace Impedance Calculator

★ Differential Impedance Calculator

★ PCB Impedance Control: Formulas and Resources - Douglas Brooks, President, UltraCAD Design, Inc.