en 4-Bio-Measurement & Bio-Instrumentation Bio-Measurement & Bio-Instrumentation Research Paper Research Paper <div style="text-align: justify;"><span style="color:#000000;"><span style="font-size:14px;"><span style="font-family:times new roman;">The Functional Electrical Stimulator design using monophasic spike-exponential waveform was proposed and described in this study. The monophasic square waveform has benefit in generating an action potential, but it could cause side effects such as toxic caused by the electrode polarization. The square waveform signal which the frequency and pulse width could be modulated was manipulated to be the monophasic spike-exponential waveform. Transformer OT240 was applied at the end of the FES system part and functioned as a voltage amplifier and DC signal isolator. On every frequency range between 5&ndash;100 Hz, the 16 peak voltage stages with the lower limit of 45 Volt and an upper limit of 400 Volt was arranged to obtain VRMS value in each stage. Characterization result shows that the produced waveform was monophasic spike-exponential with the narrow pulse width (t_1/2 = 7 &micro;s) and VRMS in the maximum frequency and peak voltage was 8.99&nbsp;Volt. This study showed that the designed FES had high VP and low VRMS, thus, it could be concluded that this FES system design could be a candidate for its application.</span></span></span></div> Functional Electrical Stimulation,Medical Rehabilitation,Monophasic Spike-Exponential Waveform,Pulse Width Modulation, 434 443 http://ijeee.iust.ac.ir/browse.php?a_code=A-10-2938-1&slc_lang=en&sid=1 A. P. Hutomo adiphutomo@gmail.com 180031947532846008274 180031947532846008274 No Biomedical Engineering Department, Postgraduate School, Universitas Airlangga, Surabaya 60286, Indonesia. I. P. Buditomo aksorojowoku@gmail.com 180031947532846008275 180031947532846008275 No Biomedical Engineering Department, Postgraduate School, Universitas Airlangga, Surabaya 60286, Indonesia. A. P. Putra alfian.pramudita@fst.unair.ac.id 180031947532846008276 180031947532846008276 No Biomedical Engineering Study Program, Department of Physics, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia. S. Suhariningsih suhariningsih@fst.unair.ac.id 180031947532846008277 180031947532846008277 No Department of Physics, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia. S. D. Astuti suryanidyah@fst.unair.ac.id 180031947532846008278 180031947532846008278 Yes Biomedical Engineering Department, Postgraduate School, Universitas Airlangga, Surabaya 60286, Indonesia.