Differential pair
From Wikipedia, the free encyclopedia
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 impotant in high-speed signal transmission, to use impedance matching techniques
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[edit] Amplifiers
Differential pair can also refer to the pair of transistors used as the input stage of a differential amplifier.
[edit] See also
- Characteristic impedance
- Impedance matching
- Twisted pair
- Low-voltage differential signalling (LVDS)
- Printed circuit board
- Transmission line
- Crosstalk (electronics)
- Electromagnetic interference
- Signal integrity
- Differential TTL
[edit] Uses of Differential Pairs
[edit] Data rates of some interfaces implemented with differential pairs
- Serial ATA 1.25 Gbps
- Hypertransport 1.6 Gbps
- Infiniband 2.5 Gbps
- PCI Express 2.5 Gbps
- Serial ATA II 2.5 Gbps
- XZUI 3.125 Gbps
- PCI Express II 5.0 Gbps
- 10 GbE 10 Gbps
[edit] 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.
