5.2 Electronic Noise Modeling

Within this chapter, we will get acquainted with the phenomena that cause the generation of noise in electronic circuits, the quantitative characterization of noise at the points of origin, the methods used for analysis of electronic circuits when noise is the subject of processing, and finally, the methods of modeling for noise circuit analysis. That will allow understanding the ways and quantities used to characterize the electronic component from noise point of view. A wide variety of components will be encompassed such as resistor, impedance, diode, BJT, JFET, MOSFET, MESFET, and a set of optoelectronic devices such as photodetectors, LED, and optocouplers. The noise amplitude is frequency dependent due to specific phenomena involved. It is also shaped by the frequency characteristic of the circuit itself. So, despite the fact that noise is experienced in the time domain, its analysis is usually performed in the frequency domain. To that aspect of the noise analysis will be devoted special attention and new quantities will be introduced which are used for noise quantification in electronic circuits and systems. Among them the most important are the noise bandwidth, the equivalent noise voltage and noise current, the signal-to-noise ratio, and the noise figure. Theory will be given accompanied with proper examples to introduce all these new terms.