“…However, due to the fact that one terminal is grounded, the grounded memristor emulator has limited features in circuit designs and applications, and is not suitable for use as a two-terminal device in more complicated circuits [20]. Compared with grounded memristor emulators, the application of floating memristor emulators is more flexible, which can be realized by various active elements, such as second-generation current conveyor (CCII) [21], operational transconductance amplifier (OTA) [22], multi outputs OTA [23], current voltage differencing transconductance amplifier (VDTA) [24], and voltage differencing current conveyor (VDCC) [25] with accompanying passive elements and possibly analog multipliers (AD633) [26]. Although some commercial memristor chips are already available on the market, e.g., Knowm.com (accessed on 9 May 2019) [27], memristor emulators have yet to be widely studied and adopted due to their lower cost.…”