## What is meant by differential pair?

In differential signaling, each signal is transmitted using a differential pair—the signal carried by one wire is the same level as the one carried by the other wire, but in opposite polarity. The signal at the receiving end is interpreted as the difference between the two lines that make up the differential pair.

## Is USB a differential pair?

In USB, signals are transmitted using differential signaling. USB 2.0 uses a single differential pair of signals, DP and DM. The USB 3.0 specification adds super-speed signaling using two additional sets of differential pairs, SSTX and SSRX, to support a separate, full-duplex connection.

**What is differential pair impedance?**

Simply put, differential impedance is the instantaneous impedance of a pair of transmission lines when two complimentary signals are transmitted with opposite polarity. For a printed circuit board (PCB) this is a pair of traces, also known as a differential pair.

### Is Ethernet a differential?

USB, HDMI, Ethernet, and many more are all routed as differential pairs and will require careful trace design and routing. In the past, this require making many manual corrections to the lengths of differential pairs to ensure they met length objectives and impedance tolerances.

### Why differential pairs are used?

The main reason differential pairs are used in long links that might cross between two boards is their immunity to ground offsets. A ground offset at AC or DC can be thought of as common-mode noise; it is a disturbance in the signal that affects each side of the pair in the same phase and magnitude.

**What is BJT differential pair?**

The typical BJT differential pair amplifier consists of a pair of transistors coupled at the emitters to a current source, having equal resistances in each collector and equal but opposite, signal sources in each base. The amplifier has several variations on this basic configuration.

#### What are differential pairs and how do they work?

To understand what differential pairs are, let’s first look at what differential signaling is. Differential signaling is a technique for electrically transmitting data using two complementary signals. The method sends the same electrical signal as a differential pair of signals, each in its own conductor.

#### What is the maximum skew introduced by the differential signaling pair?

The maximum skew introduced by the cable between the differential signaling pair (i.e., D+ and D- (TSKEW)) must be less than 100 ps and is measured as described in Section 6.7. Assuming a perfect propagation velocity (i.e. C, the speed of light), a differential length of ~2.99 cm would produce a skew of 100 ps.

**How important is the length of the differential signaling pair?**

While the length and impedance are both important, 1mm of length differential will not affect your system’s performance in any way, even for usb-2.0 high-speed. The maximum skew introduced by the cable between the differential signaling pair (i.e., D+ and D- (TSKEW)) must be less than 100 ps and is measured as described in Section 6.7.

## What is the maximum data-rate of a differential pair?

It is because of these awesome benefits that they are used in the popular and familiar communication protocols such as SATA, LVDS, PCI-E, DDR, 10gig Ethernet where the data-rates can range between 1.5Gbit/s to around 10 Gbit/s Important Rules to Adhere to When Routing Differential Pairs.