Processing of low frequency analog signals from capacitive sensors

One of the crucial problems of direct processing low-frequency analog signals from capacitive sensors is the low frequency cutoff. The miniaturization of current sensors has led to rather small sensor capacitance, typically 10 values of the order of 10^-11 F. If the signal from such a sensor, to be processed, has a frequency range extending below 100 Hz, problems start to appear due to the non-zero differential conductance seen at the signal amplifier input terminals. Moreover, some capacitive sensors require a DC polarizing voltage which, in certain cases, can be as high as 100 V or more.