{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T17:52:14Z","timestamp":1777571534677,"version":"3.51.4"},"reference-count":27,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2017,10,23]],"date-time":"2017-10-23T00:00:00Z","timestamp":1508716800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["2017R1C1B1003606"],"award-info":[{"award-number":["2017R1C1B1003606"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["2015R1C1A1A02037697"],"award-info":[{"award-number":["2015R1C1A1A02037697"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The impact of high-voltage\u2013high-frequency (HVHF) amplifiers on echo-signal quality is greater with very-high-frequency (VHF, \u2265100 MHz) ultrasound transducers than with low-frequency (LF, \u226415 MHz) ultrasound transducers. Hence, the bias voltage of an HVHF amplifier must be stabilized to ensure stable echo-signal amplitudes. We propose a bias-voltage stabilizer circuit to maintain stable DC voltages over a wide input range, thus reducing the harmonic-distortion components of the echo signals in VHF pulse-echo measurement systems. To confirm the feasibility of the bias-voltage stabilizer, we measured and compared the deviations in the gain of the HVHF amplifier with and without a bias-voltage stabilizer. Between \u221213 and 26 dBm, the measured gain deviations of a HVHF amplifier with a bias-voltage stabilizer are less than that of an amplifier without a bias-voltage stabilizer. In order to confirm the feasibility of the bias-voltage stabilizer, we compared the pulse-echo responses of the amplifiers, which are typically used for the evaluation of transducers or electronic components used in pulse-echo measurement systems. From the responses, we observed that the amplitudes of the echo signals of a VHF transducer triggered by the HVHF amplifier with a bias-voltage stabilizer were higher than those of the transducer triggered by the HVHF amplifier alone. The second, third, and fourth harmonic-distortion components of the HVHF amplifier with the bias-voltage stabilizer were also lower than those of the HVHF amplifier alone. Hence, the proposed scheme is a promising method for stabilizing the bias voltage of an HVHF amplifier, and improving the echo-signal quality of VHF transducers.<\/jats:p>","DOI":"10.3390\/s17102425","type":"journal-article","created":{"date-parts":[[2017,10,23]],"date-time":"2017-10-23T12:20:24Z","timestamp":1508761224000},"page":"2425","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":22,"title":["Bias-Voltage Stabilizer for HVHF Amplifiers in VHF Pulse-Echo Measurement Systems"],"prefix":"10.3390","volume":"17","author":[{"given":"Hojong","family":"Choi","sequence":"first","affiliation":[{"name":"Department of Medical IT Convergence Engineering, Kumho National Institute of Technology, Gumi 39253, Korea"}]},{"given":"Chulwoo","family":"Park","sequence":"additional","affiliation":[{"name":"Department of Medical IT Convergence Engineering, Kumho National Institute of Technology, Gumi 39253, Korea"}]},{"given":"Jungsuk","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Gachon University, In-cheon 21936, Korea"}]},{"given":"Hayong","family":"Jung","sequence":"additional","affiliation":[{"name":"National Institute of Health Transducer Resource Center and Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA"}]}],"member":"1968","published-online":{"date-parts":[[2017,10,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Hoskins, P.R., Martin, K., and Thrush, A. 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