Gül, Fatih; Babacan, Yunus

A universal mem-element emulator is built around a single multi-output operational-transconductance-amplifier (MO-OTA) core, one analog multiplier and one grounded resistor–capacitor pair. The same core reproduces the pinched-hysteresis dynamics of the memristor, the memcapacitor and the meminductor; only the front-end coupling and the reflection law change. An explicit state equation follows from Chua's flux–charge formulation, with the integrator voltage vC as the state. The memristor reflection law is calibrated against the Strukov–Williams compact model of an HP TiO2 device, matching its memristance excursion to 0.9% and its loop area to 5.9% over 5–100 kHz. Both active blocks are transistor-level in TSMC 0.18μm CMOS: a 15-MOSFET MO-OTA and a new 9-MOSFET four-quadrant multiplier that runs from ±0.9V with 0.16% THD and zero systematic offset. The 24-MOSFET emulator dissipates 0.61mW and preserves pinched v–i, q–v and φ–i loops from 1 kHz to 22MHz. Robustness spans 45 process–voltage–temperature corners and a 500-run Monte-Carlo analysis with per-device threshold-mismatch; the modulated element stays positive-definite in every run (σ/μ=9.7%). In the Itoh–Chua oscillator it yields a double-scroll attractor with λmax=0.311, against 0.276 for an ideal memristor. It stays fully floating, needs no mutator or switching network, and uses the smallest active-block count among universal emulators.

Yesil, Abdullah; Babacan, Yunus

This paper introduces a flux-controlled memristor emulator circuit which can be controlled by electronically both fix and variable parts of memristance. Here, the fix part symbolizes the average memristance value, and the variable part refers to the changing part around the fixed part. Another advantage of the presented circuit is that it is composed of only four transistors and one grounded capacitor which provides memory to the circuit. For this reason, it can be said that the circuit is very simple, compatible with both VLSI implementation, and suitable for implementation on breadboards using discrete circuit elements. The proposed circuit can be operated at MHz frequency ranges and a strong pinched hysteresis loop can be seen at these frequencies. Finally, all simulation and experimental results are compatible with previous studies.

Korkmaz, Muhammet Oguz; Babacan, Yunus; Yesil, Abdullah

Due to their many advantages, memelements are a prominent research topic among scientists. Nevertheless, creating emulator circuits is necessary because of the issues with memelements availability. In this paper, a new CCII-based meminductor emulator circuit is presented. The circuit is composed of a few active and passive circuit elements. In order to demonstrate the performance of the proposed circuit, we applied to different analysis types such as at different operating frequencies, temperatures, Monte Carlo, worst case analysis and non-volatility test. In addition to the simulation results, the circuit was built using discrete circuit components, experimental results were examined. The proposed meminductor emulator circuit has a variety of significant advantages, including a simple construction, suitability for implementation in discrete circuits, and great performance in the analysis of both simulation and experimental results.

Gebeşoğlu, Durmuş; Kuloğlu, Mustafa; Ertay, Agah Oktay; Şimşek, Serkan

In this study, two low-profile wideband spiral antennas that are backed by Circular Artificial Magnetic Conductors (C-AMC) are proposed for V/UHF bands. Rather than using a C-AMC design that has single resonance frequency, different C-AMC structures that have different resonance frequencies are used beneath corresponding active regions of spiral antenna, such that frequency independent radiation characteristics are achieved. The C-AMC surface is designed to aim of covering the entire frequency band of antenna so that frequency regions where reflection phase of C-AMC rings are between +90° and −90° will follow each other. It is observed that using frequency-independent C-AMC and a thin absorber between C-AMC and outer region of spiral antenna element provides wideband antenna characteristics and improves axial ratio of antennas. Proposed Antenna 1 in this paper has low-profile (0.47λ0 ×0.47λ0 ×0.055λ0) at 300 MHz and high gain at frequencies between 300 MHz and 950 MHz. An absorbing material is used at the inner wall of the closed cavity to improve performance of Proposed Antenna 2 at lower frequencies. In this manner, 0 dBi realized gain transition point is achieved at 235 MHz. Proposed Antenna 2 has also low-profile (0.37λ0 ×0.37λ0 ×0.043λ0) at 235 MHz.

Babacan, Yunus; Yesil, Abdullah; Tozlu, Omer Faruk; Kacar, Firat

Memristive systems have become popular as a research field after the experimental realization of a memristor by the HP Labs research team. Researchers have demonstrated the synaptic behavior of the memristor in addition to its nonlinear and nonvolatile characteristics. Synapses play an important role in the learning process and spike-timing-dependent plasticity (STDP) is a fundamental synaptic learning rule. Because of problems with finding the memristor on the market as a discrete circuit element, researchers have designed many types of memristor circuits to emulate memristors. However, no information is available about the STDP behavior of these designed memristor emulators. This paper investigated the STDP property of some basic memristor circuits and the mathematical and simulation results demonstrated that none of them could support the STDP learning rule.

Konal, Mustafa; Kacar, Firat; Babacan, Yunus

Memcapacitors are become one of the research interest after the realization of memristors. Many researchers focused on the designing memcapacitor emulator because of some fabrication difficulties of this new element. In this paper, Voltage Differencing Current Conveyor (VDCC) based memcapacitor emulator is developed. This emulator is composed of two VDCCs and can be electronically controllable. To show the operation performance of the proposed circuit, some analyses and memcapacitor based associative learning circuit are given. TSMC 0.18 µm process parameters are used to simulate the memcapacitor. The circuit is also implemented on breadboard using discrete circuit elements. Both theoretical and simulation results are good agreement when compared previous studies.

Tozlu, Ömer Faruk; Kaçar, Fırat; Babacan, Yunus

The nervous system, besides its complexity, offers advantages such as high speed, very low energy consumption and high fault tolerance required in electronic systems, and has led researchers to work on more efficient biologically similar electronic systems. Neuristors are electronic neurons which are mimicking biological neurons' behavior and candidate to implement circuits that are different from the classical circuits. Neuristor based electronically controllable logic gates are proposed in this paper. Various logic gate circuits based on neuristor can be found in literature. The originality of this paper is that the proposed circuit can be operated as a different logic gate on the same schematic by changing only circuit parameters. The used simple neuristor circuit is built using a memristor that is different from classical TiO2 sandwich structure, Mott memristor, and can produce commonly used spike types. The inputs and outputs of all logic circuits are current pulses and voltage spike trains, respectively. Here, if the circuit produces zero voltage or spike voltage train, the outputs are called ‘0’ or ‘1’, respectively. Combinational logic applications such as adder, encoder, multiplexer, etc. have been implemented to show that the proposed circuit can operate like standard CMOS logic gates.

Yesil, Abdullah; Babacan, Yunus; Kacar, Firat

In this paper, we have presented a Dual-Output Operational Transconductance Amplifier (DO-OTA) and Differential Voltage Current Conveyor (DVCC)-based fully floating emulator which enables the memristor current to flow in both directions when used with other circuit elements. The proposed memristor consists of only one DO-OTA, one DVCC, one grounded capacitor that is attractive for an integrated circuit, and two PMOS transistors operating as an electronic resistor. The proposed fully floating memristor emulator includes two very important features: (1) the fixed and variable memductance parts of the circuit are electronically adjustable, and (2) both incremental and decremental circuit behaviors can be obtained without altering the circuit topology. The circuit was laid using the Cadence Spectre Analog Environment with TSMC 0.18 µm process parameters and occupied a layout area of only 119 µm × 90 µm. The post-layout simulation results for the memristor circuit were obtained for different operating frequencies and all simulations were fully compatible with the experimental memristor behaviors. Finally, the memristor circuit was built on a breadboard using discrete circuit elements, and all experimental results were also compatible with the expected memristor characteristics.

Yesil, Abdullah; Babacan, Yunus; Kacar, Firat

In this study, a simple memristor circuit using only one Voltage Differencing Current Conveyor (VDCC), two PMOS transistors and one grounded capacitor, is designed. The presented memristor exhibits electronically controllable characteristics, which are superior to its counterparts. Both the memductance value and the operating frequency can be electronically tuned through voltage sources. The proposed memristor, which occupies 42.2 µm × 27.5 µm area excluding the area of the capacitor, is laid by using Cadence Environment using TSMC 0.18 µm process parameters. In addition, the proposed memristor is implemented by using discrete circuit elements on the breadboard and detailed analyses are given by changing the values of the discrete circuit elements. All results are compatible with the previous studies.

Yildirim, Melih; Babacan, Yunus; Kacar, Firat

In this paper, special memristor circuit and memristive retina network structure for analogue image processing have been presented. The new developments on memristor element have opened various possibilities due to its being in nano-scale and having nonlinear behavior. The proposed memristor emulator consists of only one Operational Transconductance Amplifier (OTA) and two MOS transistors which are operated in sub-threshold region. The memristor fuse structure is obtained by connecting two proposed memristor emulators. In the second section of our paper, we proposed a circuit block which is composed of 16 × 16 pixels retinomorphic memristive grid to maintain a smoothed and edges preserved image. All simulation results for both proposed memristor circuits and retinomorphic grid are obtained as expected.