A family of AC amplifiers for ultra‐low frequency operation

A family of capacitively coupled alternating current (AC) amplifiers featuring ultra-low (below 1 Hz) corner frequency is presented. This achieved by using high-gain devices which actively boost feedback resistance and thus reduce frequency. procedure often termed, though with a different purpose, as “bootstrapping.” The proposed architectures are very general admit several possible practical implementations. To demonstrate their usefulness, the circuits implemented two operational (OA), but other active such transconductance (OTAs) can be alternatively used. All have been theoretically analyzed, extensively simulated measured, exhibiting high-pass cutoff frequencies low 30 mHz.