Most of the research on fractional-order (FO) systems has been presented for passive realization of FO capacitors and inductors. In this paper, an active realization of a FO capacitor or a constant-phase element (CPE) is presented in the form which can be realized as an integrated circuit. The realization is demonstrated using OTA-C structures in AMS 0.35um C35B4 technology. We propose the realization of active constant phase elements using OTAs having MOS transistors in the saturation region. The linearization of each OTA is applied by source degeneration. We use standard approximation such as second-order continuous fraction expansion (CFE) to design three non-integer orders of 1/3, 1/2 and 2/3. We propose tuning method using different bias currents of OTAs to obtain desired phase characteristics of the CPE.