**6. Conclusions**

The bootstrapping effect has been applied to a bulk-driven MOS transistor in order to enhance its voltage gain up to a value close to unity. As a result, a voltage follower with improved noise and linearity responses and able to operate in extremely low voltage conditions can be obtained. This voltage buffer has been used, along with a low-voltage pseudo-resistor, to implement a linearized transconductor, which is the basic building block of a second-order *Gm*-*C* BPF aimed at multi-frequency bioimpedance analysis. These circuits have been designed in a 180 nm CMOS process to operate with a supply voltage as low as 0.6 V. The performance of the filter is compatible with the requirements of IoT applications, especially in terms of power consumption, and is comparable to other state-of-the-art solutions previously reported.

**Author Contributions:** Conceptualization, J.M.C. and C.A.d.l.C.-B.; methodology, J.M.C. and C.A.d.l.C.-B.; software, J.M.C. and C.A.d.l.C.-B.; formal analysis, J.M.C. and C.A.d.l.C.-B.; investigation, J.M.C. and C.A.d.l.C.-B.; resources, J.M.C. and C.A.d.l.C.-B.; data curation, J.M.C. and C.A.d.l.C.-B.; writing—original draft preparation, J.M.C. and C.A.d.l.C.-B.; writing—review and editing, J.M.C. and C.A.d.l.C.-B.; visualization, J.M.C. and C.A.d.l.C.-B.; supervision, J.M.C. and C.A.d.l.C.-B.; project administration, J.M.C. and C.A.d.l.C.-B.; funding acquisition, J.M.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** Work funded by projects RTI2018-095994-B-I00, from MCIN/AEI/10.13039/501100011033, and IB18079, from *Junta de Extremadura* R&D Plan, and by Fondo Europeo de Desarrollo Regional (FEDER) Una manera de hacer Europa.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interests.
