An apparatus configured to identify a material having an electric charge, the apparatus having: an inverting gain amplifier including a first field-effect transistor (FET) coupled to a second FET; wherein a gate of the first FET is configured to sense the electric charge and an output of the amplifier...http://www.google.de/patents/US8052931?utm_source=gb-gplus-sharePatent US8052931 - Ultra low-power CMOS based bio-sensor circuit
