Very-low frequency capacitively coupled AC amplifier with a current feedback operational amplifier

In this paper, we propose the idea of using transimpedance amplifiers, in lieu of operational amplifiers (OAs) or transconductance amplifiers (OTAs) to design capacitively coupled AC amplifiers. The idea is demonstrated with a current feedback operational amplifier (CFOA) as an active element, which is actually an architecture consisting of voltage buffers and current copiers (mirrors). This last characteristic is further exploited to make the corner frequency of the AC amplifier tunable by means of bootstrapping low-valued resistors with the output buffer. It is particularly suited to achieve very-low corner frequencies as needed in applications such as bio- or seismic signals. The idea is demonstrated with simulations and experimental results with a discrete implementation.