- the basics of burst noise or "popcorn noise" experienced in RF and electronic circuits.
Burst noise is not as widely known as other forms of noise in electronic and RF circuits.
Burst noise consists of sudden step like transitions between two or more levels.
This form of noise may not affect some circuits much, but others it can provide some particular problems and issues.
Burst noise basics
Burst noise, or as it is sometimes called, Popcorn noise, or random telegraph signal, RTS, consists of sudden step-like transitions between two or more levels.
The burst noise steps may be as high as several hundred microvolts, at random and unpredictable times.
Each shift in offset voltage or current can last for several milliseconds, and the intervals between pulses tend to be in the low audio range - typically less than about 100 Hz.
Burst noise, or popcorn noise was an issue when the first operational amplifiers were introduced. It made a noise like cooking popcorn if sent to a loudspeaker - hence the name.
The most common cause for this noise in ICs is believed to be the random trapping and release of charge carriers at thin film interfaces. Also defect sites in bulk semiconductor crystal can give rise to burst noise. In some cases the effect can have a greater effect than others. It is particularly severe when it affects an MOS gate or in a bipolar base region. In these cases the output effect can be significant.
These defects can be caused by manufacturing process issues: e.g. heavy ion implantation, or unintentional side-effects such as surface contamination. As the effect is a result of a manufacturing issue, offending ICs can be detected and removed during manufacture.
By Ian Poole
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