Another kind of resistor noise, which depends at the same time. The most prominent contributor to noise appearing in amplifiers is the use of low-wattage resistors of carbon composition. An important factor that can be extremely large at low frequencies is flicker noise, since of its 1/f frequency characteristic. Wire-wound resistors do not experience this type of noise, only resistors consisting of films or carbon particles. in the resistor flows no current,. In correspondence with an increase of current, the flicker noise increases. This comports that for low noise concerns, keeping low the direct and alternate currents is a must. The fabric as well as the geometry of the resistor can have a great effect on the flicker noise. So, doubling the resistor power rating, that rises the size and area, the 1/f noise generated throughout the resistor is consequently conspicuously lessened.
Shot noise is yet another type of electronic noise. The discrete flow of electrons is the cause of shot noise. In resistor applications, shot noise is often not considered relevant. However in semi-conductors it can be a more significant source of electric noise. The amount of noise depends on the current, but is independent of the temperature. Therefore it can become a dominating kind of noise at very low temps.
Noise in active components, in which electrons are arriving randomly at electrodes, is most of the times more significant with respect to noise within passive devices, but the noise appearing in certain resistors, primarily the out of date types made of carbon, is sensibly great since the building of the resistor and its composition. A low-noise first stage is a must for any amplifier of significant gain, since noises happening at the input will definitely be subject to the full gain of the amplifier, and all resistors which are used in this first stage will be called low-noise types.
make use of metal films or are wirewound should be specified, because they have reduced noise values with respect to other kinds. As temperature is increased, the real quantity of noise voltage rises, so that to achieve low-noise performance, the cooling of input stages is very useful. The signal bandwidth is also important, in fact, the smaller the bandwidth that a signal employs the lower is the noise in all the resistors in which the signal flows. A resistor’s noise level is normally reported in terms of microvolts of noise per volt of applied voltage for a standard one MHz bandwidth.
Check out noise in resistors
