Measurement of 1/f Noise in Carbon Composition and Thick Film Resistors

Thermal noise and 1/f noise are known to exist in carbon composition (CC) and thick film (TF) resistors. A circuit involving a differential instrumentation op-amp was used to measure the noise of a resistor under test. The noise spectra of these resistors were measured using a dynamic signal analyzer that performs an auto-correlation Fourier transform from the time domain to the frequency domain to determine the amount of 1/f noise in the spectra. Various noise-canceling techniques were implemented, such as nitrogen inerting a grounded metal box containing the circuit. A dc voltage was applied across the resistor under test in each measurement. The results show that CC and TF resistors produce 1/f noise and have a voltage dependence on the noise, which varies as 1/ . The exponent γ was determined for each 1/f-noise-producing resistor. The resistors produce an ac noise power in the zeptowatt/Hz-attowatt/Hz range (10-10 Watts/Hz). In the future, additional thermal noise measurements and analysis will be carried out on resistors, in addition to building a 1/f-noise-producing guitar effects pedal.