Low-frequency noise measurements of high-Tc superconducting films: effect of DC capacitor in experimental setup

Often a transformer is used with a DC-blocking capacitor as a voltage gain stage in experimental setups that measure low-frequency noise in high-T_c superconducting films. Presented is a system response analysis to show that the value of the DC-blocking capacitor determines the validity of the lower frequency limit of the measured noise voltage spectral density data.