On Operational Transconductance Amplifiers Research Articles

Design of Two Stage OTA based Sixth Order Butter-worth Low Pass Filter using CMOS 180nm Technology

This paper shows the design of 6th order Butter-worth low pass filter based on operational trans-conductance amplifier (OTA). The designing and simulation results are obtained using Cadence Virtuoso tool with 180nm (0.18μm) technology. The simulation results of OTA have a gain of about 97.3dB. The simulation results of butter-worth low pass filter for 1.25V supply voltage and 20μA biasing current gives -96.4mdB gain and 2.9GHz bandwidth for a frequency range of 100Hz to 10GHz. The results are presented in this paper.

Impedance-mode capacitance multiplier with OTA-based flipped voltage follower for high accuracy and large multiplication factor

A capacitance multiplier with large multiplication factor, increased accuracy, and class AB operation is presented. The multiplier is an impedance mode implementation consisting of a Flipped Voltage Follower based on Operational Transconductance Amplifiers (OTA). This gives the possibility to offer rail-to-rail operation and class AB operation to drive demanding loads depending on the application. In addition, one of the OTAs is designed to offer a transconductance gain based on passive resistors and achieve increased accuracy in the multiplication factor by means of proper layout techniques. The circuit was implemented in a 0.5µm technology and has multiplication factors of 10, 100, 1k and 10k, a power dissipation of 0.56mW and a silicon area of 0.059mm2. Simulation and experimental results of the multiplier demonstrate the proper operation.

CMOS OTA-Based Filters for Designing Fractional-Order Chaotic Oscillators

Fractional-order chaotic oscillators (FOCOs) have shown more complexity than integer-order chaotic ones. However, the majority of electronic implementations were performed using embedded systems; compared to analog implementations, they require huge hardware resources to approximate the solution of the fractional-order derivatives. In this manner, we propose the design of FOCOs using fractional-order integrators based on operational transconductance amplifiers (OTAs). The case study shows the implementation of FOCOs by cascading first-order OTA-based filters designed with complementary metal-oxide-semiconductor (CMOS) technology. The OTAs have programmable transconductance, and the robustness of the fractional-order integrator is verified by performing process, voltage and temperature variations as well as Monte Carlo analyses for a CMOS technology of 180 nm from the United Microelectronics Corporation. Finally, it is highlighted that post-layout simulations are in good agreement with the simulations of the mathematical model of the FOCO.

Low-Voltage and Low-Power Analog Multiplier/Divider Using OTA Based on DTMOS Transistor

A low-voltage and low-power current mode analog multiplier/divider design is presented in this paper. The multiplier/divider is based on operational transconductance amplifier (OTA) utilizing dynamic threshold MOS (DTMOS) structure and consists of only three OTAs. The circuit has the ability of consuming low power and requiring low voltage power supplies. 0.13µm IBM CMOS technology parameters are used to simulate the suggested multiplier/divider design and the simulation results are obtained using LTspice program. The current mode analog multiplier/divider architecture consumes only 12.07nW and requires ±0.2V of supply voltages thanks to employing DTMOS transistor. The simulation results agree well with the expected results.

Chaotic circuit with OTA based memristor on image cryptology

In this study, a new chaotic system and its analog circuit design have been introduced. The circuit of chaotic system has only a memristor, an inductor, a capacitor and a negative resistor. The proposed memristor emulator circuit is based on Operational Transconductance Amplifier (OTA) and it consists of multipliers, resistors, a capacitor and a current conveyor apart from OTAs. We have shown the chaotic behavior of our system with both numerical analyses done in MATLAB environment and an analog circuit analyses using LTspice simulation software. In addition to chaotic (pseudo-periodic) behavior, the periodic spiking behavior of our proposed system by changing a system parameter is also presented. The image cryptology method is carried out to prevent the unauthorized distribution of information and data. In image encryption part, an algorithm is suggested to provide confusion (pixel position permutation) and diffusion (pixel value transformation) operations on the image. A pixel swap method for both row and column is preferred as confusion operation and a logical XOR method for both row and column is done as diffusion operation on the pixels of the image. In order to decrypt the encrypted image, the reversed swap and the reversed XOR operations have been performed. In this way, image encryption and decryption schemes using a chaotic system with OTA based memristor are successfully carried out. Moreover, the security analyses with the help of histogram analysis, correlation coefficient analysis of two adjacent pixels, information entropy analysis and initial condition sensitivity analysis have been done in order to prove that our suggested algorithm is robust against different statistical attacks and exhaustive attack.

On the design of OTA-C based field programmable analog arrays for continuous time low frequency applications

This work focuses on proposing FPAA architecture based on operational transconductance amplifier (OTA) as the basic block for low frequency continuous time signal processing. Two FPAA architectures are presented after a step by step development of the design structure. The architectures eliminate the use of switches for signal routing, instead they allow reconfigurability using a selecting network composed of OTAs. The proposed architectures demonstrate flexibility in architecture allowing the expansion of the basic structure. Both architectures allow the implementation of individual independent circuits with an option of cascading if required. Multiple filter circuits can be mapped on the FPAA with independent control and reconfigurability of gain, bandwidth, and notch frequency, thus allowing the use of the FPAA as a filter bank. As for the provided cascading feature, it allows the implementation of a system or a set of cascaded filters as desired by designer. Validation of proposed FPAA architecture and its characteristics is examined through simulation on LTspice using 90 nm CMOS technology with supply voltage of ±0.6 V. A single 4th-order lowpass filter is implemented first and then a combination of amplifier, notch filter and lowpass filter is implemented. Simulation results of the filters on proposed FPAA is compared to results acquired from simulation of the circuits alone (off-FPAA) showing excellent agreement between both results, hence confirming the proposed FPAA architecture.

Special issue on SoC and AI processors

Special issue on SoC and AI processors

Electronically controllable third-order quadrature sinusoidal oscillator employing CMOS-OTAs

This paper describes a voltage mode third-order quadrature sinusoidal oscillator (TOQSO) based on operational transconductance amplifiers (OTAs). The proposed configuration uses three OTAs and three grounded capacitors. Outputs of two voltage mode sinusoids with 90° phase difference are found in the proposed oscillator circuit. The condition of oscillation and frequency of oscillation are independently electronically controllable by separate transconductances of the OTAs. The performance of TOQSO is tested by SPICE (version 16.5) simulation using TSMC 0.18 µm technology parameters and experimental results employing CA3080 type IC OTAs have been presented to confirm the workability of the proposed new configuration.

Impact on Gain and Noise : ECG Amplifier & Comb Filter Design using OTA

The research paper ventures a novel modelling strategy of finite gain and noise of an electrocardiogram (ECG) amplifier at 0.18, 0.5 and 0.9 micron standard CMOS technologies respectively. An active comb filter is used to design the amplifier for removing the selected frequencies of numerous signals. The presented filter is configured with only Operational Transconductance Amplifiers (OTAs) and capacitors that makes it apt for implementation of monolithic integrated circuits (ICs). The relevance of this analog circuit is verified for a suitable test signal of 60 Hz as in the ECG signal. Using Cadence Virtuoso analog design environment, the effect of transistor channel length and width is examined for analysis of noise and bandwidth. It is observed that the performance in terms of noise and gain considerably increases for advanced technology node. However, for a suitable supply of bias current, a portable ECG system can also provide an improved bandwidth performance of advanced CMOS technology.

Electronically Tunable Fractional Order All Pass Filter

In this paper, an electronically tunable fractional order all pass filter (FOAPF) based on operational transconductance amplifier (OTA) is presented. It uses two OTAs and single fractional order capacitor (FC) of non-integer order α to provide FOAPF of α order. Two different values of α, in particular 0.5 and 0.9, for FC are taken for investigation. The functionality of the proposal is verified through SPICE simulations using TSMC 0.18 μm Complementary Metal Oxide Semiconductor (CMOS) process parameters. Simulated and theoretical frequency and time domain responses are found to be in close agreement.

Electronically Tunable Fractional Order Filter

In this paper, an electronically tunable resistorless fractional order filter (FOF) based on operational transconductance amplifier (OTA) is presented. It uses two fractional capacitors (FC) of same order and provides fractional order low-pass filter and fractional order band-pass filter responses simultaneously. Mathematical formulations are outlined for various critical frequencies and transfer function sensitivities for presented FOF. The FCs of orders 0.5 and 0.9 are considered for illustrating the proposal. The FCs are realized using the fourth-order continued fraction expansion-based RC ladder and are characterized using SPICE simulations. Functional verification of presented FOF with FC of orders 0.5 and 0.9 is exhibited through SPICE simulations. The OTA is implemented using $$0.5\,\upmu \hbox {m}$$ CMOS technology model parameters. Electronic tunability of half power and right-phase frequencies of presented FOF is achieved through bias current variation of OTA. The transfer functions’ sensitivity with respect to various circuit parameters is also examined through simulations, and it is found that the values remain well within unity for most of the circuit parameters. Furthermore, the presented FOF is attractive from integration viewpoint as it achieves tunability via bias current variation in contrast to tuning through resistor variation in existing FOFs.

A spiking and bursting neuron circuit based on memristor

In this paper, we propose two emulator circuits. Firstly, we present a novel memristor emulator based on operational transconductance amplifier (OTA) which is different from classical TiO2 memristor. This memristor emulator has a threshold switching mechanism. Secondly, we create a novel neuron circuit using proposed memristor, which is capable of generating spiking and bursting firing behaviors, with a biologically plausible spike shapes. The behavior of this neuron circuit can be adjusted by changing only one external biasing voltage. This neuron circuit mimics the behavior of cortical neurons, such as regular spiking (RS), intrinsic bursting (IB), chattering (CH) and fast spiking (FS). Proposed emulator circuits are compatible with VLSI systems and they can also be implemented by using discrete circuit components for different applications.

Negative current feedback OTA with application to 250 MHz Gm-C filter

A 4th-order low-pass Gm-C filter for high speed wireless/wireline system is realized in 0.18 μm CMOS process. The high speed filter is designed based on operational transconductance amplifier (OTA)...

OTA-based monostable multivibrators with current tuning properties

This paper presents two new monostable multivibrator circuits based on operational transconductance amplifiers (OTAs). Both configurations use two OTAs with a few passive components. The first circuit is operated under the positive-edge triggering mode, and the second one is a negative-edge triggering mode design. The width and height of the output pulse are tunable via the bias current of OTAs or an external resistor. The proposed monostable multivibrators are more compact compared to the existing designs. In order to verify the feasibility of the presented circuits, prototypes are implemented, using commercial ICs and discrete components. In addition, the circuit principles are described and analyzed in detail. Experimental results are close to the theoretical analysis.

OTA based frequency tuning system with reduced effect of DC offsets

An on-line tuning system based on the master–slave technique is proposed in this paper. Each stage of the system is realized by employing only operational transconductance amplifiers (OTAs). The most significant advantage of the introduced topology is the reduction of the influence of the dc offset terms which are critical about the performance of such systems. In addition, an attractive benefit is the suitability for implementing the resulted configurations in both integrated and discrete-component forms using only the same type of active element. The validation of the proposed topology is achieved through simulation and experimental results.

Particle detector tunable monolithic Semi-Gaussian shaping filter based on transconductance amplifiers

An IC semi-Gaussian shaper architecture for X-rays silicon strip detectors is presented. The specific structure is based on operational transconductance amplifiers (OTAs) and was implemented using an alternative design technique. The shaper was designed and fabricated in a 0.35μm process by Austria Mikro Systeme and provides continuous variable operating bandwidth in a relatively low-frequency region, capability that indicates it as an optimum selection for a variety of readout applications. Analysis is supported by measurement results confirming the advantageous shaping filter performance. The circuit appears to be low power providing 530μW power dissipation, while the output noise performance is 167μV (rms) for an operating bandwidth of 260kHz. Extensive experimental results concerning the total harmonic distortion and the dynamic range of the circuit also confirm its satisfactory performance.

Design guidelines and comparison of detector readout front end integrated S-G shapers using transconductance circuits

An analysis of readout front end electronics semi-gaussian (S-G) shapers is carried out. Innovative design methodology is proposed and an advanced filter design technique based on operational transconductance amplifiers (OTA) is used, in order to implement fully integrated structures. Three respective novel CMOS shaper topologies are designed and compared in terms of noise performance, total harmonic distortion, dynamic range and power consumption as to examine which is the most preferable in readout applications. Analysis is supported by simulations results using SPICE in a 0.6 µm process by the Austria Mikro Systeme (AMS). The optimum implementation appears to be the OTA based cascade shaper structure with the inductor simulation. The specific shaper implementation is used in a fully integrated preamplifier-shaper system for a space application silicon strip detector of 2 pF capacitance. The readout system achieves an equivalent noise charge of 327 electrons at 1.7 µs peaking time in −40°C.

Detailed study of particle detectors OTA-based CMOS Semi-Gaussian shapers

An analysis of readout front-end electronics Semi-Gaussian (S-G) shapers is carried out. An innovative design methodology is proposed and advanced filter design techniques based on Operational Transconductance Amplifiers (OTA) are used. Five CMOS shaper topologies are designed using OTAs and compared in terms of noise performance, total harmonic distortion, dynamic range and power consumption in order to examine which is the most preferable in readout applications. Although all shaper architectures are fully integrated, they exhibit a large peaking time. The results are obtained from SPICE simulations for implementations in a 0.6 μm process of Austria Mikro Systeme (AMS).

A new OTA-C current-mode biquad filter with single input and multiple outputs

A new current-mode biquad-filtering circuit with single input and multi-outputs based on operational transconductance amplifier (OTA) is presented using three OTAs, two grounded capacitors and one grounded resistor, it can simultaneously realize second-order lowpass, bandpass, highpass, notch and allpass filters. The characteristic parameters can be adjusted orthogonally by a bias current of OTA and all capacitors are gounded. Morever, the circuit enjoys low sensitivities.

OTA-Based Sine-to-Triangular Wave Converter

A sine-to-triangular wave converter based on operational transconductance amplifiers (OTAs) is proposed in this paper. The realization method exploits a hyperbolic tangent behavior of an OTA to convert from a sine wave to a triangular wave. The proposed circuit provides a simple configuration and employs only OTAs as the active elements. This scheme can be operated in both a voltage-controlled mode and a current-controlled mode. The performances of the proposed circuit are discussed in detail and confirmed by the experimental results.