Electronically Tunable Full Wave Precision Rectifier Using DVCCTAs

This work presents a voltage mode scheme of a full-wave precision rectifier circuit using an analog building block differential voltage current conveyor transconductance amplifier (DVCCTA) including five NMOS transistors. The proposed design is essentially suited for low voltage and high-frequency input signals. The operation of the proposed rectifier design depends upon the region of operation of NMOS transistors. The output waveform of the presented rectifier design can be made electronically tunable by controlling the bias voltage. The functional correctness and verification of the presented design are performed using 0.25-µm TSMC technology under the supply voltage of ±1.5 V. The absence of a resistor leads to a minimal parasitic effect. To obtain further insight on the robustness of the circuit, a Monte Carlo simulation and corner analysis are also presented. The circuit is verified experimentally by incorporating a breadboard model with the help of commercially available ICs CA3080 (operational transconductance amplifier) and AD844AN (current feedback operational amplifier) and offers remarkable compliance with both theoretical and simulation outcomes. The presented design has been laid out on Cadence virtuoso, which consumes a chip area of 9044 µm2.

Realization of Inverse Active Filters Using Single Current Differencing Buffered Amplifier

The authors introduce a new single current differencing buffered amplifier (CDBA) based inverse filter configuration. By appropriate selection of admittances, different inverse filter circuits like inverse high-pass (IHP) circuit, inverse low-pass (ILP) circuit, inverse band-reject (IBR) circuit and inverse band-pass (IBP) circuit can be realized from the same configuration. The capacitors used here are grounded/virtually grounded for all the realizations. The performances of the proposed filters have been judged by using CMOS structure of CDBA with TSMC 0.35 µm technology as well as by using the available IC of current feedback operational amplifier (CFOA) i.e. AD844 based CDBA. The simulation results agreed well with the theoretical results. Monte-Carlo simulation has also been performed to check the robustness of the proposed configuration.

Optimal Modelling of (1 + α) Order Butterworth Filter under the CFE Framework

This paper presents the optimal rational approximation of (1+α) order Butterworth filter, where α ∊ (0,1) under the continued fraction expansion framework, by employing a new cost function. Two simple techniques based on the constrained optimization and the optimal pole-zero placements are proposed to model the magnitude-frequency response of the fractional-order lowpass Butterworth filter (FOLBF). The third-order FOLBF approximants achieve good agreement to the ideal characteristic for six decades of design bandwidth. Circuit realization using the current feedback operational amplifier is presented, and the modelling efficacy is validated in the OrCAD PSPICE platform.

A Novel Floating/Grounded Meminductor Emulator

Meminductor is a nonlinear two-terminal element with storage energy and memory ability. To date, meminductor element is not available commercially as memristor and memcapacitor are. Therefore, it is of great significance to implement a meminductor emulator for breadboard experiment. In this paper, a flux-controlled floating/grounded meminductor emulator without a memristor is presented. It is built with commercially available off-the-shelf electronic devices. It consists of single operational transconductance amplifier (OTA), single multiplier, two second-generation current conveyors (CCIIs), single current-feedback operational amplifier (CFOA) and single operational amplifier. Using OTA device introduces an additional control parameter besides frequency and amplitude values of applied voltage to control the area of pinched hysteresis loop of meminductor. Mathematical model of proposed emulator circuit is given to describe the behavior of meminductor circuit. The breadboard experiment is performed using CA3080, AD844, AD633J and LM741 for OTA, CCII–CFOA, multiplier and operational amplifier, respectively. Simulation and experimental test results are given to verify the theoretical analyses. Frequency-dependent pinched hysteresis loop is maintained up to 5 kHz. The presented meminductor emulator tends to work as ordinary inductor for higher frequencies.

Electronic Tuning Square-Wave Generators with Improved Linearity Using Operational Transresistance Amplifier

Two new electronic tuning current-mode square-wave generators are introduced in the ensuing paper. In the first proposed square-wave generator circuit, one Operational Trans-resistance Amplifier (OTRA) and two passive components are involved, along with two NMOS depletion mode transistors. This circuit generates a square-wave with almost equal and fixed duty cycles. The second proposed circuit is able to control both on-duty and off-duty cycles independently with the help of two passive components, two NMOS depletion mode transistors, and two diodes connected to the circuit. The frequency of the proposed circuits can be adjusted with the passive components connected to the circuit. Moreover, electronic tuning can also be achieved with the proposed circuits. The measured results that are included in the paper show the linear variation of a time period as compared with existing OTRA based square waveform generator. The performance of the proposed circuits is examined while using SPICE models. These circuits are built on a laboratory breadboard using commercially available Current Feedback Operational Amplifier (AD844 AN) and passive components are connected externally and tested for square waveform generation. The obtained results demonstrate good agreement with the theoretical values.

A Multifunctional Voltage Mode Fractional Order Filters using a Single CFOA

A multifunction voltage mode fractional order filter structure is described using a single current feedback operational amplifier (CFOA). This configuration realizes three fractional order filters (FOFs) namely fractional order low pass (FOLP), fractional order band pass (FOBP) and fractional order high pass (FOHP) filters. The performance of the proposed structure has been verified through PSPICE and MATLAB simulation results using macro model of AD844 type CFOA.

Dual Output Sinusoidal Oscillator Using Second Generation Current Controlled Conveyor

Second Generation Current Controlled Conveyor (CCCII) based tunable Dual Output Sinusoidal Oscillator (MSO) is proposed. It consists of three CCCIIs, a resistor and two grounded capacitors. By tuning external DC bias current, the oscillator frequency and commencement of its oscillations are controlled electronically. The proposed circuit is verified using PSPICE simulator and also on laboratory breadboard using commercially available integrated circuits Current Feedback Operational Amplifier (AD844AN) and Operational Transconductance Amplifier (LM13600) at a supply rail voltage of ±6 V. Further its nonlinearities, sensitivities, performance characteristics are also verified. Comparison of the proposed topology with the ongoing methods are also undertaken. PSPICE simulation results are verified with a low supply voltage of ±1 V, temperature analysis, analysis by using Montecarlo method and finally Total Harmonic Distortion (THD) is also demonstrated.

A memristor-based chaotic-masking for analog spread-spectrum communication

<span>This paper presents a simple chaotic-masking system. The system uses a chaos generator built around a grounded memristor. The memristor is emulated using the current-feedback operational amplifier (CFOA). At the sending end the signal is masked by adding chaos. At the receiving end the signal is recovered by subtracting the chaos. The performance of proposed system is investigated using sinusoidal and square wave signals.</span>