Introduction to the advantages of differential signaling

The oscilloscope high-voltage differential probe is an indispensable part of the oscilloscope's use process. It is mainly used as a signal transmission link to transmit the signal under test to the oscilloscope in a complete and reliable manner for further measurement and analysis. There are many types of probes that match these oscilloscopes, including passive probes (including high-voltage probes, transmission line probes), active probes (including active single-ended probes, active differential probes, etc.), current probes, optical probes, etc. Each type of probe has its own advantages and disadvantages, so each has its own applicable occasions. Among them, active probes are widely used in the field of high-speed digital measurement due to their high bandwidth, small input capacitance, and small ground loop.

Probes can be generally divided into passive probes and active probes. Users of wide-bandwidth oscilloscopes and active probes also need to choose between single-ended probes and differential probes. The pair of traces that carry differential signals is called differential traces. We tell you about differential probes. Compared with ordinary single-ended signal traces, differential signals have obvious advantages in the following three aspects:

1. Strong anti-interference ability, because the coupling between the two differential traces is very good. When there is noise interference from the outside, they are almost coupled to the two lines at the same time, and the receiving end only cares about the difference between the two signals. Therefore, the external common-mode noise can be canceled to a large extent.

2. It can effectively suppress EMI. For the same reason, due to the opposite polarity of the two signals, the electromagnetic field radiated by them can cancel each other out. The tighter the coupling, the less the electromagnetic energy vented to the outside world.

3. Timing positioning, because the switch change of the differential signal is located at the intersection of the two signals, unlike ordinary single-ended signals that rely on the high and low threshold voltages to determine, it is less affected by the process and temperature, and can reduce the error in the timing. It is also more suitable for circuits with low amplitude signals. The current popular LVDS refers to this small-amplitude differential signal technology.

The structural characteristics of the differential signal require that the corresponding test equipment must also be a differential topology. Therefore, the differential probe has become the mainstream accessory of modern oscilloscopes.