{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T15:10:22Z","timestamp":1773328222287,"version":"3.50.1"},"reference-count":35,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2022,6,29]],"date-time":"2022-06-29T00:00:00Z","timestamp":1656460800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper proposes a duty-cycle electronically tunable triangular\/square wave generator using LT1228 commercially available ICs for capacitive sensor interfacing. The generator comprises two LT1228s, a grounded resistor, and a grounded capacitor. The circuit provides two output signals which are triangular and square waves. Both signals are regulated by adjusting the current bias. Likewise, the amplitude of the triangular signal can be tuned electronically without affecting the frequency. In addition, the square wave can independently control the linear duty cycle via tuning the voltage. Experiment results confirm the performance of the proposed circuit that the amplitude of the triangular wave, frequency, and duty cycle are linearly controllable via current or voltage, which do not affect each other. The duty cycle, the amplitude of the triangular wave, and frequency have maximum errors of \u00b11.60%, \u00b13.33%, and \u00b12.55%, respectively.<\/jats:p>","DOI":"10.3390\/s22134922","type":"journal-article","created":{"date-parts":[[2022,6,29]],"date-time":"2022-06-29T22:43:28Z","timestamp":1656542608000},"page":"4922","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Duty-Cycle Electronically Tunable Triangular\/Square Wave Generator Using LT1228 Commercially Available ICs for Capacitive Sensor Interfacing"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7447-1783","authenticated-orcid":false,"given":"Phamorn","family":"Silapan","sequence":"first","affiliation":[{"name":"Department of Electrical Engineering, Faculty of Engineering and Industrial Technology, Sanam Chandra Palace Campus, Silpakorn University, Nakhonpathom 73000, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pawich","family":"Choykhuntod","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, Faculty of Engineering and Industrial Technology, Sanam Chandra Palace Campus, Silpakorn University, Nakhonpathom 73000, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1687-9350","authenticated-orcid":false,"given":"Rapeepan","family":"Kaewon","sequence":"additional","affiliation":[{"name":"Department of Electrical Engineering, Faculty of Engineering and Industrial Technology, Sanam Chandra Palace Campus, Silpakorn University, Nakhonpathom 73000, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1261-0917","authenticated-orcid":false,"given":"Winai","family":"Jaikla","sequence":"additional","affiliation":[{"name":"Department of Engineering Education, School of Industrial Education and Technology, King Mongkut\u2019s Institute of Technology Ladkrabang, Bangkok 10520, Thailand"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,6,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2174","DOI":"10.1109\/TIM.2008.2006729","article-title":"Current Conveyor-Based Square\/Triangular Waveform Generators With Improved Linearity","volume":"58","author":"Pal","year":"2009","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Torteanchai, U., Manman, S., Kumngern, M., and Lerkvaranyu, S. (2019, January 10\u201313). Square\/Triangular Wave Generator Using Single Bulk-Driven FDCCII. Proceedings of the 2019 16th International Conference on Electrical Engineering\/Electronics, Computer, Telecommunications and Information Technology (ECTI-CON), Pattaya, Thailand.","DOI":"10.1109\/ECTI-CON47248.2019.8955221"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"152931","DOI":"10.1016\/j.aeue.2019.152931","article-title":"Special type of current conveyor-based Schmitt trigger in novel design of triangular waveform generator","volume":"112","author":"Sotner","year":"2019","journal-title":"AEU-Int. J. Electron. Commun."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"980","DOI":"10.1109\/19.872917","article-title":"Limitations of a relaxation oscillator in capacitance measurements","volume":"49","author":"Liu","year":"2000","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1060","DOI":"10.1002\/cta.2268","article-title":"A CCII-based non-inverting Schmitt trigger and its application as astable multivibrator for capacitive sensor interfacing","volume":"45","author":"Marcellis","year":"2017","journal-title":"Int. J. Circuit Theory Appl."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"877","DOI":"10.1007\/s00034-011-9373-y","article-title":"A Simple Schmitt Trigger Circuit with Grounded Passive Elements and Its Application to Square\/Triangular Wave Generator","volume":"31","author":"Minaei","year":"2012","journal-title":"Circuits Syst. Signal Process."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Tudosa, I., Picariello, F., Balestrieri, E., De Vito, L., and Lamonaca, F. (2019, January 4\u20136). Hardware Security in IoT era: The Role of Measurements and Instrumentation. Proceedings of the 2019 II Workshop on Metrology for Industry 4.0 and IoT (MetroInd4.0&IoT), Naples, Italy.","DOI":"10.1109\/METROI4.2019.8792895"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1934","DOI":"10.1109\/TIM.2005.853684","article-title":"The noise performance of a high-speed capacitive-sensor interface based on a relaxation oscillator and a fast counter","volume":"54","author":"Gasulla","year":"2005","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"186175","DOI":"10.1109\/ACCESS.2019.2961640","article-title":"Novel Schmitt Trigger and Square-Wave Generator Using Single Current Amplifier","volume":"7","author":"Alzaher","year":"2019","journal-title":"IEEE Access"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"5051","DOI":"10.1109\/TIM.2019.2954236","article-title":"A Low-Power Tunable Square-Wave Generator for Instrumentation Applications","volume":"69","author":"Panda","year":"2020","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"3369","DOI":"10.1109\/TIM.2011.2128490","article-title":"Tunable Square-Wave Generator for Integrated Sensor Applications","volume":"60","author":"Kar","year":"2011","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"152","DOI":"10.1016\/j.procs.2016.05.040","article-title":"A Current-mode Square\/Triangular Ware Generator Based on Multiple-output VDTAs","volume":"86","author":"Siripruchyanun","year":"2016","journal-title":"Procedia Comput. Sci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"206","DOI":"10.1016\/j.aeue.2017.12.004","article-title":"A novel linear square\/triangular wave generator with tunable duty cycle","volume":"84","author":"Chaturvedi","year":"2018","journal-title":"AEU-Int. J. Electron. Commun."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"634","DOI":"10.1016\/j.mejo.2014.04.003","article-title":"A current-\/voltage-controlled four-slope operation square-\/triangular-wave generator and a dual-mode pulse width modulation signal generator employing current-feedback operational amplifiers","volume":"45","author":"Chien","year":"2014","journal-title":"Microelectron. J."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"320","DOI":"10.3390\/app5030320","article-title":"Synthesis of Cascadable DDCC-Based Universal Filter Using NAM","volume":"5","author":"Tran","year":"2015","journal-title":"Appl. Sci."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Chen, H.P., Hwang, Y.S., and Ku, Y.T. (2017). Voltage-mode and current-mode resistorless third-order quadrature oscillator. Appl. Sci., 7.","DOI":"10.3390\/app7020179"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Chen, H.P., and Yang, W.S. (2017). Electronically Tunable Current Controlled Current Conveyor Transconductance Amplifier-Based Mixed-Mode Biquadratic Filter with Resistorless and Grounded Capacitors. Appl. Sci., 7.","DOI":"10.3390\/app7030244"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Herencsar, N., Koton, J., and Hanak, P. (2017). Universal Voltage Conveyor and its Novel Dual-Output Fully-Cascadable VM APF Application. Appl. Sci., 7.","DOI":"10.3390\/app7030307"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Sotner, R., Jerabek, J., Prokop, R., Kledrowetz, V., and Polak, J. (2017). A CMOS Multiplied Input Differential Difference Amplifier: A New Active Device and Its Applications. Appl. Sci., 7.","DOI":"10.3390\/app7010106"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Faseehuddin, M., Herencsar, N., Albrni, M.A., and Sampe, J. (2021). Electronically Tunable Mixed-Mode Universal Filter Employing a Single Active Block and a Minimum Number of Passive Components. Appl. Sci., 11.","DOI":"10.3390\/app11010055"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Vatavu, M., Nastasescu, V., Turcu, F., and Burda, I. (2019). Voltage-controlled synthetic inductors for resonant piezoelectric shunt damping: A comparative analysis. Appl. Sci., 9.","DOI":"10.3390\/app9224777"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Wang, S.F., Chen, H.P., Ku, Y., and Chen, P.Y. (2019). A CFOA-based voltage-mode multifunction biquadratic filter and a quadrature oscillator using the CFOA-based biquadratic filter. Appl. Sci., 9.","DOI":"10.3390\/app9112304"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Sotner, R., Domansky, O., Jerabek, J., Herencsar, N., Petrzela, J., and Andriukaitis, D. (2020). Integer-and fractional-order integral and derivative two-port summations: Practical design considerations. Appl. Sci., 10.","DOI":"10.3390\/app10010054"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Wang, S.-F., Chen, H.-P., Ku, Y., and Li, Y.-F. (2021). High-Input Impedance Voltage-Mode Multifunction Filter. Appl. Sci., 11.","DOI":"10.3390\/app11010387"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"3449","DOI":"10.1007\/s00034-015-0015-7","article-title":"Comparison of Two Solutions of Quadrature Oscillators With Linear Control of Frequency of Oscillation Employing Modern Commercially Available Devices","volume":"34","author":"Sotner","year":"2015","journal-title":"Circ. Syst. Signal Processing"},{"key":"ref_26","first-page":"281","article-title":"Catalog of Realizations for DXCCII using Commercially Available ICs and Applications","volume":"21","author":"Maheshwari","year":"2012","journal-title":"Radioengineering"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Kubanek, D., Koton, J., Dvorak, J., Herencsar, N., and Sotner, R. (2021). Optimized Design of OTA-Based Gyrator Realizing Fractional-Order Inductance Simulator: A Comprehensive Analysis. Appl. Sci., 11.","DOI":"10.3390\/app11010291"},{"key":"ref_28","first-page":"85","article-title":"Practical Floating Capacitance Multiplier Implementation with Commercially Available IC LT1228s","volume":"51","author":"Tangsrirat","year":"2021","journal-title":"Inf. MIDEM"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Jaikla, W., Adhan, S., Suwanjan, P., and Kumngern, M. (2020). Current\/voltage controlled quadrature sinusoidal oscillators for phase sensitive detection using commercially available IC. Sensors, 20.","DOI":"10.3390\/s20051319"},{"key":"ref_30","first-page":"2962","article-title":"One input voltage and three output voltage universal biquad filters with orthogonal tune of frequency and bandwidth","volume":"11","author":"Wai","year":"2021","journal-title":"Int. J. Electr. Comput. Eng."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Wang, S.-F., Chen, H.-P., Ku, Y., and Lee, C.-L. (2020). Versatile Voltage-Mode Biquadratic Filter and Quadrature Oscillator Using Four OTAs and Two Grounded Capacitors. Electron, 9.","DOI":"10.3390\/electronics9091493"},{"key":"ref_32","unstructured":"(2022, May 11). Linear Technology, LT1228: 100MHz Current Feedback Amplifier with DC Gain Control. Available online: https:\/\/www.analog.com\/media\/en\/technical-documentation\/data-sheets\/1228fd.pdf."},{"key":"ref_33","unstructured":"Abramowitz, I.A.M. (1970). Stegun, Handbook of Mathematical Functions: With Formulas, Graphs, and Mathematical Tables."},{"key":"ref_34","unstructured":"(2022, June 16). Honeywell, HCH-1000 Series: Capacitive Humidity Sensors. Available online: https:\/\/media.digikey.com\/pdf\/Data%20Sheets\/Honeywell%20Sensing%20&%20Control%20PDFs\/HCH-1000%20Series.pdf."},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Jaikla, W., Buakhong, U., Siripongdee, S., Khateb, F., Sotner, R., Silapan, P., Suwanjan, P., and Chaichana, A. (2021). Single Commercially Available IC-Based Electronically Controllable Voltage-Mode First-Order Multifunction Filter with Complete Standard Functions and Low Output Impedance. Sensors, 21.","DOI":"10.3390\/s21217376"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/13\/4922\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T23:40:31Z","timestamp":1760139631000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/13\/4922"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,6,29]]},"references-count":35,"journal-issue":{"issue":"13","published-online":{"date-parts":[[2022,7]]}},"alternative-id":["s22134922"],"URL":"https:\/\/doi.org\/10.3390\/s22134922","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,6,29]]}}}