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tags:
  - resource
created: 2026-05-30 11:26
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## Summary

One channel is inverted in differential signaling to provide exceptional **noise immunity** and to **double the signal strength.** 

In differential signaling, the data is transmitted across two separate conductors: one carries the original signal, and the other carries an inverted (mirror-image) copy. Here is why this is done: 

1. Superior Noise Cancellation

External electrical interference (like electromagnetic noise from nearby wires or power supplies) usually affects both wires in a pair equally. This is known as **common-mode noise**. 

- At the receiving end, a differential amplifier subtracts the two signals to determine the true data.
- Because the noise exists equally on both wires, the subtraction mathematically cancels the noise out completely.

2. Doubled Signal Strength

When the receiver subtracts the inverted signal from the original signal, it yields double the voltage difference. 

- For example, if the original signal is \(+1V), the inverted signal is \(-1V).
- The voltage difference is: \(+1V - (-1V) = 2V).
- This creates a stronger overall signal, making it much easier to detect data accurately even in noisy environments or over very long distances.

3. Reduced Electromagnetic Interference (EMI)

Because the two wires run tightly parallel to each other, the equal and opposite magnetic fields they generate cancel each other out. This prevents the cables from radiating their own electronic noise, allowing for high-speed transmission with minimal cross-talk.

The two differential wires are **twisted** so that any EMI signal reaches both wires at essentially the same time.  This is referred to as a **twisted pair**.

Differential signalling does not affect noise cancellation. [Balanced lines](https://en.wikipedia.org/wiki/Balanced_line "Balanced line") with differential receivers will reject noise regardless of whether the signal is differential or single-ended, but since balanced line noise rejection *requires* a differential receiver, differential signalling is often used on balanced lines. 
## References

- [Why Twisted Pair?](https://www.youtube.com/watch?v=RVzM-b3okH0)
- [Differential Signaling]()
