Advantages of differential signaling | disadvantages of differential signaling

This page covers advantages and disadvantages of differential signaling. It mentions differential signaling advantages or benefits and differential signaling disadvantages or drawbacks.

What is differential signaling?

• The transmission of two signals which are complementary over identical matched traces or wires is special case of two wire signaling known as differential signaling.
• A differential signal by definition is known as balanced signal. It is measured by difference between positive and negative side of the signal. They have lower distortion compare to single ended circuits as depicted below in figure-1.
• It is used to electrically transmit information using two complementary signals.

differential signaling

• The receiver circuit responds to electrical difference between two signals instead of difference between signal wire and GND (used in single ended signaling). Figure shows working of differential signaling. As shown input signals are combined where as noise signals are substrated by differential receiver.
• Examples of differential signaling is found in analog signaling and digital signaling.
• Analog differential signaling: Balanced Audio
• Digital differential signaling: Twisted pair, PCIe interface, DisplayPort, USB, HDMI, RS-422, RS-485

Benefits or advantages of differential signaling

Following are the benefits or advantages of differential signaling:
➨It is resistant to EM (Electromagnetic) interference as differential signals are transmitted on balanced lines.
➨It also helps in minimizing electronic crosstalk.
➨It can be used for high speed transmission lines with good quality due to noise elimination and less radiation. Hence Common mode rejection as well as improved power supply rejection can be achieved.
➨Higher overall signal swings can be achieved.
➨It offers inherent cancellation of even order harmonics. Some pre-distortion techniques are employed to reduce odd harmonics.

Drawbacks or disadvantages of differential signaling

Following are the drawbacks or disadvantages of differential signaling:
➨Differential signals have one obvious disadvantage over single ended signals. They require two traces instead of one, or twice as much board area. When multiple signals are transmitted the number of conductors are more than single ended signaling. For example, in differential signaling 8 signals require 16 conductors and a ground conductor to have common ground between sender and receiver. In this case, the single ended signaling requires only 9 conductor wires.

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