Differential pair impedance最好

"Differential pair impedance" is a term used in the context of electrical engineering, particularly in the design of printed circuit boards (PCBs) and high-speed digital systems. It refers to the characteristic impedance of a differential pair of conductors, which is the opposition to the flow of differential current between the two conductors.

The differential pair impedance is an important parameter in the design of high-speed digital circuits because it affects the quality of the signal transmission. A differential pair consists of two conductors that carry equal and opposite signals. The difference between the signals is the differential signal, which is used to cancel out noise and improve signal integrity.

The impedance of a differential pair is typically designed to be 50 ohms or 100 ohms, depending on the specific requirements of the system. The impedance is determined by the physical dimensions of the conductors and the properties of the material between them, such as the dielectric constant and the thickness of the insulation.

To achieve the desired impedance, the width and spacing of the conductors in the differential pair must be carefully controlled. The width of the conductors is typically chosen to be as wide as possible while still fitting within the available space on the PCB, and the spacing between the conductors is typically chosen to be as small as possible while still providing adequate clearance for manufacturing tolerances and thermal expansion.

The differential pair impedance can be calculated using the formulas provided by the transmission line theory, which relate the impedance to the physical dimensions of the conductors and the properties of the material between them. However, the actual impedance may differ from the calculated value due to manufacturing tolerances, temperature variations, and other factors.

Therefore, it is common to measure the differential pair impedance using specialized equipment, such as a vector network analyzer (VNA), and to adjust the design accordingly. This is particularly important in high-speed digital systems, where even small variations in impedance can lead to signal integrity issues such as reflections, crosstalk, and timing skew.