**6. Conclusions**

By means of a systematic analysis, the possibility of realizing VCII-based oscillators is studied and demonstrated. The investigation results in a pair of new canonic oscillators based on VCII−. However, it is shown that, using the systematic approach, no oscillator configuration is possible using VCII+. The two found oscillator configurations are the only possible ones which use only two resistors, two capacitors and a single VCII−. Compared to Op-Amp-based oscillators, designed using the same systematic approach which employs two capacitors and four resistors, the proposed VCII-based oscillator is preferred in terms of low number of capacitors and resistances. Another interesting feature of the found VCIIbased oscillator is that the produced sinusoidal output signal is easily available through the low output impedance Z port, while the CCII-based oscillators designed using the same systematic approach requires an additional voltage buffer for practical use. Simulations and experimental results using AD844 as VCII are reported to validate the theory.

A comparison with oscillator topologies based on different ABBs, with particular attention to canonic topologies, is reported in Table 4. The table reports the type of active building block (ABB) the oscillator is based on, the number of active and passive components, specifying how many of them are grounded, the availability of a quadrature output and the independence of oscillation condition from oscillation frequency that allows tuning the oscillator acting on a single component. It has to be noted that the independence from the oscillation condition on oscillation frequency often requires additional passive (and sometimes also active) components, thus resulting in non-canonic topologies. Notable exceptions are the oscillators of [21,26] that use complex ABBs with gain, whose value contributes to satisfying the oscillation condition.


**Table 4.** Comparative table of sinusoidal oscillator topologies.

Op-Amp: operational amplifier; OTA: operational transconductance amplifier; CCII: second generation current conveyor; FTFN: four terminal floating nullor; CDTA: current differencing transconductance amplifier; OTRA: operational transresistance amplifier; CCCCTA: current controlled current conveyor transconductance amplifier; CCIII: third generation current conveyor; UVC: universal voltage conveyor; VDTA: voltage dependent transconductance amplifier; CFOA: current feedback operational amplifier; CDBA: current differencing buffered amplifier; VCII: second generation voltage conveyor.

**Author Contributions:** Conceptualization, M.S. and G.B.; methodology, G.B. and F.C.; software, G.B.; validation, G.F., P.T., V.S. and L.P.; formal analysis, M.S. and F.C.; investigation, P.T. and V.S.; resources, V.S. and G.F.; data curation, V.S. and L.P.; writing—original draft preparation, L.P. and G.B.; writing—review and editing, V.S., G.B., L.P., M.S., G.F., F.C. and A.T.; visualization, F.C. and L.P.; supervision, L.P., G.F., V.S. and P.T.; project administration, G.F., V.S. and A.T.; funding acquisition, V.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** The work did not receive any external funding.

**Data Availability Statement:** No new data were created or analyzed in this study. Data sharing is not applicable to this article.

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