## 4 Conclusions  
This research presents a low-voltage, low-power CDTA, implemented using the bulk-driven MOS transistor technique to achieve a low supply voltage. The proposed CDTA is applied in a current-mode universal filter to demonstrate its performance. This universal filter can realize transfer functions for low-pass, band-pass, high-pass, band-stop, and all-pass responses within a single topology. All transfer functions are implemented with high output impedance, which is essential for current-mode circuits. The circuit addresses challenges related to inverting input signals, input signal matching, and the need for multiple input signals. Additionally, the natural frequency of the filters can be electronically controlled, providing an easy method to compensate for temperature variations. The CDTA and its application were designed using 0.18 \(\upmu\)m CMOS technology.  
Conceptualization, F.K., M.K. and T.K.; methodology, F.K., M.K. and T.K.; software, F.K. and M.K.; validation, F.K. and M.K.; formal analysis, T.K. and M.K.; investigation, F.K., M.K. and T.K.; resources, M.K.; data curation, F.K. and M.K.; writing--original draft preparation, F.K., M.K., T.K. and J.V.; writing--review and editing, F.K., M.K., T.K. and J.V.; visualization, F.K. and M.K.; supervision, F.K. and M.K.; project administration, F.K. and M.K.; funding acquisition, M.K. All authors have read and agreed to the published version of the manuscript.  
This work was supported in part by the University of Defence within the Organization Development Project VAROPS.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Factor** & **Proposed 2025** & **[25] 2024** & **[29] 2019** & **[31] 2022** & **[32] 2019** \\ \hline Number of active devices & 2-CDTA & 4-CDTA & 8-INV & 8-OTA & 3-VCII, 1-ICB \\ \hline Realization & 0.18 \(\upmu\)m CMOS & 0.18 \(\upmu\)m CMOS & 32 nm CNTFET & 0.18 \(\upmu\)m CMOS & 0.18 \(\upmu\)m CMOS \\ \hline Number of passive devices & 2-C & 2-C, 2-R & 2-C & 2-C & 2-C, 3-R \\ \hline Filter mode & CM (MIMO) & CM (MISO) & CM (MISO) & MM (MIMO) & TIM (SIMO) \\ \hline Total number of filter responses & 19 & 12 & 5 (CM) & 5 (CM) & 5 \\ \hline Electronic control of \(\omega_{o}\) & Yes & Yes & Yes & Yes & No \\ \hline All passive devices & Yes & Yes & Yes & Yes & No \\ grounded & & & & & \\ \hline Without inverted/double & & & & & \\ input conditions/input- & Yes & No & No & No & Yes \\ matching condition & & & & & \\ \hline High-output impedance & Yes & Yes & Yes & Yes & - \\ \hline Power supply (V) & 0.45 & 0.5 & \(\pm\)0.2 & \(\pm\)0.3 & \(\pm\)0.9 \\ \hline Power dissipation (\(\upmu\)W) & 1.098 & 3.39 & \(447\times 10^{-3}\) & 5.77 & \(1.47\times 10^{3}\) \\ \hline Natural frequency (Hz) & 2.66 \(\times\)\(10^{3}\) & 104.7 & \(1.1\times 10^{6}\) & \(5\times 10^{3}\) & \(1.5\times 10^{6}\) \\ \hline Integrated noise (pA) & 42.35 & 38.32 & - & - & - \\ \hline THD (\%) & 0.8@40 nA & 0.936@150 nA & \textgreater{}1.16 & 0.8@100 nA & 3.6@5 \(\upmu\)A \\ \hline Dynamic range (dB) & 61 & 68.86 & - & 53.2 & - \\ \hline Verification of result & Sim. & Sim. & Sim. & Sim. & Sim. \\ \hline \hline \end{tabular} Note: ICB = Inverting Current Buffer, INV = Inverter, CNTFET = Carbon Nanotube Field-Effect Transistor, MM = Multi-Mode, TIM = Transimpedance Mode, MIMO = Multiple-Input Multiple-Output, MISO = Multiple-Input Single-Output, SIMO = Single-Input Multiple-Output.  
\end{table}
Table 4: Comparison of the proposed current-mode universal filter with those of some previous filters.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
**Conflicts of Interest:** The authors declare no conflicts of interest.