Spectroscopic effects of distributed-line phenomena in integrated feedback resistors for charge-sensitive pre-amplifiers

The distributed capacitive coupling of high-valued resistors with ground planes modifies their effective impedance and power spectral density of noise, especially at high frequency. This effect is clearly visible in poly-silicon resistors inside integrated circuits. When such resistors are used in the feedback network of Charge Sensitive Pre-amplifiers an excess noise arises with a non-white noise spectral density. The effect is a worsening of the spectroscopic resolution. The relevance of such effect with respect to the conventional noise sources is discussed in different practical cases.