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Flicker noise is a type of electronic noise with a 1/''f'', or pink power spectral density. It is therefore often referred to as 1/''f'' noise or pink noise, though these terms have wider definitions. It occurs in almost all electronic devices, and can show up with a variety of other effects, such as impurities in a conductive channel, generation and recombination noise in a transistor due to base current, and so on. == Properties == 1/''f'' noise in current or voltage is usually related to a direct current, as resistance fluctuations are transformed to voltage or current fluctuations via Ohm's law. There is also a 1/f component in resistors with no DC current through them, likely due to temperature fluctuations modulating the resistance. This effect is not present in manganin, as it has negligible temperature coefficient of resistance. In electronic devices, it shows up as a low-frequency phenomenon, as the higher frequencies are overshadowed by white noise from other sources. In oscillators, however, the low-frequency noise can be mixed up to frequencies close to the carrier which results in oscillator phase noise. Flicker noise is often characterized by the corner frequency ''f''c between the region dominated by the low-frequency flicker noise and the higher frequency "flat-band" noise. MOSFETs have a higher ''f''c (can be in the GHz range) than JFETs or bipolar transistors, which is usually below 2 kHz for the latter. It typically has a Gaussian distribution and is time-reversible. It is generated by a linear mechanism in resistors and FETs, but a non-linear mechanism in BJTs and diodes.〔 The flicker noise voltage power in MOSFET is often modeled as , where ''K'' is the process-dependent constant, is the oxide capacitance in MOSFET devices, ''W'' and ''L'' are channel width and length respectively.〔Behzad Razavi, Design of Analog CMOS Integrated Circuits, McGraw-Hill, 2000, Chapter 7: Noise.〕 This is an empirical model, and generally thought to be an oversimplification. Flicker noise is found in carbon composition resistors, and in thick film resistors where it is referred to as ''excess noise'', since it increases the overall noise level above the thermal noise level, which is present in all resistors. In contrast, wire-wound resistors have the least amount of flicker noise. Since flicker noise is related to the level of DC, if the current is kept low, thermal noise will be the predominant effect in the resistor, and the type of resistor used may not affect noise levels, depending on the frequency window. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Flicker noise」の詳細全文を読む スポンサード リンク
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