S.Sh. Rekhviashvili1, D.S. Gaev2

1 Institute of Applied Mathematics and Automation, KBSC RAS (Nalchik, Russia)

2 Kabardino-Balkarian State University named after H.M. Berbekov (Nalchik, Russia)

1 rsergo@mail.ru; 2 dahir@mail.ru

Problem statement. Existing radio circuits can be divided into linear, nonlinear and parametric. All of them allow electronic adjustment of certain parameters, which is carried out using such variable capacitors as variconds and varicap diodes. The disadvantages of these capacitors are small values of capacitance overlap, nonlinear dependence of the electrical capacitance on the voltage supplied directly to the device, dependence of the electrical capacitance on temperature, and radiation susceptibility. In this regard, an urgent practical task is the development of efficient variable capacitors based on significantly new physical principles. This article solves such a problem.

Aim. Theoretical and experimental study of the possibility of using an optocoupler as a variable capacitor in radio frequency circuits.

Results. For the first time, it was proposed to use an optocoupler as a capacitive element for tuning radio frequency circuits. Using the example of a relaxation generator, the high efficiency of the functioning of an optocoupler in a new quality is demonstrated. It has been shown that the optocoupler provides a significantly larger range of control of the generation frequency than a standard varicap diode. Formulas for frequency-dependent electrical conductivity and electrical capacitance of the optocoupler output transistor are derived. Relaxation generators based on the K561LA7 microcircuit with control in the feedback circuit using a KV115A varicap and a PC817 transistor optocoupler were experimentally studied. The dependence of the output capacitance of the photodetector on the input electrical power of the optocoupler emitter was measured. The theoretical analysis is based on the concepts of barrier and diffusion capacitances.

Practical significance. The results obtained can be used to create electronic equipment for various purposes. An optocoupler can be used as a tuning element in high-frequency electrical circuits, in radio and wire communications, in local oscillators, and in special measuring devices.

The work was carried out according to the state order of the Ministry of Science and Higher Education of the Russian Federation (subjects no. 075-01560-23-07, no. 122041800014-1).

Rekhviashvili S.Sh., Gaev D.S. Application of an optocoupler for capacitive regulation in radio frequency circuits. Radiotekhnika. 2025. V. 89. № 6. P. 104−113. DOI: https://doi.org/10.18127/j00338486-202506-10 (In Russian)

1. Baskakov S.I. Radiotehnicheskie cepi i signaly. M.: URSS. 2024. 528 s. (in Russian).
2. Vendelin G.D., Pavio A.M., Rohde U.L., Rudolph M. Microwave circuit design using linear and nonlinear techniques. 3rd edition. John Wiley & Sons Inc. 2021. 1174 p.
3. Szczepaniak Z.R., Galwas B.A. Photo-devices for optical controlling of microwave circuits. Journal of Telecommunications and Information Technology. 2001. №3. P. 86–94. https://doi.org/10.26636/jtit.2001.3.62.
4. Zel'din E.A. Impul'snye ustrojstva na mikroshemah. M.: Radio i svjaz'. 1991. 160 s. (in Russian).
5. Tuchkevich V.M., Grehov I.V. Novye principy kommutacii bol'shih moshhnostej poluprovodnikovymi priborami. L.: Nauka. 1988. 117 s. (in Russian).
6. Grehov I.V., Mesjac G.A. Poluprovodnikovye nanosekundnye diody dlja razmykanija bol'shih tokov. UFN. 2005. T. 175. № 7. S. 735–744. https://doi.org/10.3367/UFNr.0175.200507c.0735 (in Russian).
7. Phillips T.J., Gordon N.T. Negative diffusion capacitance in Auger-suppressed HgCdTe heterostructure diodes. Journal of Electronic Materials. 1996. V. 25. № 8. P. 1151-1156. https://doi.org/10.1007/BF02655001.
8. Butcher K.S.A., Tansley T.L., Alexiev D. An instrumental solution to the phenomenon of negative capacitances in semiconductors. Solid-State Electronics. 1996. V. 39. № 3. P. 333-336. https://doi.org/10.1016/0038-1101(95)00143-3.
9. Jones B.K., Santanat J., McPherson M. Negative capacitance effects in semiconductor diodes. Solid State Communications. 1998. V.107. № 2. P. 47-50. https://doi.org/10.1016/S0038-1098(98)00162-8.
10. Zhu C.Y., Feng L.F., Wang C.D., Cong H.X., Zhang G.Y., Yang Z.J., Chen Z.Z. Negative capacitance in light-emitting devices. Solid-State Electronics. 2009. V.53. P.324–328. https://doi.org/10.1016/j.sse.2009.01.002.
11. Feng L.F., Li Y., Zhu C.Y., Cong H.X., Wang C.D. Negative terminal capacitance of light emitting diodes at alternating current (AC) biases. IEEE Journal of quantum electronics. 2010. V. 46. № 7. P. 1072-1075. https://doi.org/10.1109/JQE.2010.2043337.
12. Li Y., Wang C.D., Feng L.F., Zhu C.Y., Cong H.X., Li D., Zhang G.Y. Elucidating negative capacitance in light-emitting diodes using an advanced semiconductor device theory. Journal of Applied Physics. 2011. V. 109. P. 124506. http://dx.doi.org/10.1063/1.3597831.
13. Bourim E.-M., Han J.I. Electrical characterization and thermal admittance spectroscopy analysis of InGaN/GaN MQW blue LED structure. Electron. Mater. Lett. 2015. V. 11. № 6. P. 982-992. https://doi.org/10.1007/s13391-015-5180-0.
14. Patent № 2799113 (RF). Sposob povyshenija bystrodejstvija tranzistorov i tranzistornyh integral'nyh shem. Rehviashvili S.Sh., Narozhnov V.V. Prioritet ot 18.03.2022 (in Russian).
15. Al'tudov Ju.K., Gaev D.S., Pshu A.V., Rehviashvili S.Sh. Bipoljarnyj tranzistor s opticheskoj nakachkoj. Mikrojelektronika. 2023. T. 52. № 6. C. 489-496. https://doi.org/10.31857/S0544126923600240 (in Russian).
16. Nikitin A.B., Habitueva E.I. Sverhshirokopolosnyj SVCh-generator, upravljaemyj naprjazheniem. Radiotehnika. 2018. T. 82. № 1. S. 4-9  (in Russian).
17. Kaganov V.I., Fam K. SVCh-fil'tr s upravljaemoj polosoj propuskanija. Radiotehnika. 2019. T. 83. № 1. S. 70-72. DOI: 10.18127/j00338486-201901-08 (in Russian).