Operational Transconductance Amplifier Circuit Research Articles

Nature inspired algorithm based design of near ideal fractional order low pass Chebyshev filters and their realization using OTAs and CCII

Fractional order filters offer greater freedom of design and a precise control over stopband attenuation in electronic circuits and systems. This paper presents the design of a fractional order low pass Chebyshev filter (FOLCF) that achieves near-ideal response characteristics. The methodology introduced utilizes metaheuristic optimization methods, including particle swarm optimization, firefly algorithm, and grey wolf optimization. These techniques are employed to precisely adjust the filter coefficients for the orders (1+α), (2+α), and (3+α). The adjustment is carried out by comparing the desired behaviour of the FOLCF with generalized fractional order low pass transfer functions. Throughout these instances, the parameter α is varied within the range of (0, 1). The designed filters are then tested and compared on the basis of various factors. Simulation results demonstrate that the designed filters closely follow the behaviour of an ideal Chebyshev filter with maximum passband and stopband magnitude errors being −31.93 dB and −52.74 dB respectively for (1+α) order filters. These values for (2+α) and (3+α) order FOLCF have been observed to be −30.04 dB and −55.91 dB; −17.72 dB and −49.52 dB respectively. Furthermore, it has been observed that the proposed work outperforms existing state-of-the-art approaches in various aspects, including magnitude error, stopband attenuation, and cut-off frequency. The stability of the designed filters has been verified through stability analysis. Additionally, practical feasibility of the proposed FOLCF is demonstrated through SPICE simulations for α = [0.2,0.5,0.8] using second generation current conveyor (CCII) and operational transconductance amplifier (OTA) based topologies while approximating the constant phase element using fifth order continued fraction expansion. The SPICE implementations closely follow the behaviour of ideal filter with −48.67 dB and −62.8 dB as mean square errors for CCII and OTA circuits respectively, showcasing the proposed filters' superiority and practical applicability in advanced electronic design.

Implementation of OTA in 90nm Technology with Bandgap Reference Application

Operational Transconductance Amplifier (OTA) is the basic building block of Analog circuit with linear input/output characteristics. Because it associates closely linked parameters like noise and settling performance, the current design methodologies for two-stage OTAs frequently result in sub-optimal solutions. The study discusses the implementation of an Operational transconductance amplifier (OTA) with a bandgap reference (BGR) circuit and its importance in providing a stable and accurate reference voltage for various analog and digital circuits. The combination of OTA and BGR provides a stable and accurate reference voltage that can be used in various analog and digital circuits. OTAs are used to drive high capacitive loads. To scale the dimensions of Complementary Metal Oxide Semiconductor (CMOS) technology requires proportional scaling, also taking supply voltage into consideration. In addition to the simplicity and strong performance that the Band Gap Reference (BGR) achieves as a load for the OTA circuit, the architecture of OTA with BGR as load is easily adaptable to attain high accuracy. Because the performance of the used amplifier has a significant impact on the OTA’s performance, consideration must be given to the design and its architecture. Therefore, it is essential to carry out a comparison analysis in order to get the optimal results of the outputs of OTA having BGR as the load.

Operational Transconductance Amplifier Designed with Experimental Omega-Gate Nanowire SOI MOSFETs

The nanowire omega-gate technology is one of the possible technologies to replace the FinFET one in the semiconductor chip market. The omega-gate nanowire SOI MOSFET is considered a triple plus gate device, near the gate-all-around performance (figure 1) [1]. Due to the omega gate structure this device presents a better gate to channel electrostatic coupling than the FinFET devices, resulting in a greater immunity to short channel effects [1,2].The Operational Transconductance Amplifier (OTA) is a frequently used analog block in the integrated circuits. The studied OTA consists in a two-stage amplifier, where the first stage is a differential amplifier with active load and the second one is a common source amplifier, as can be seen in figure 2. This analog block is biased through the current source and the bias current is mirrored for each stage. In addition, negative feedback is used between the first and second stages with a compensation capacitor (miller capacitor) in order to stabilize the amplifier response.In this work, an OTA circuit is designed with SOI omega-gate nanowire experimental transistors. In order to find the best device to be used in the project, some measurements were carried out of several nanowire devices with different channel lengths (ranging from 20 nm to 200 nm). The schematic structure of the measured devices is presented in figure 3 [2]. Basic device parameters such as: transconductance (gm), output conductance (gd), Early voltage (VEA), threshold voltage (VT), transistor efficiency (gm/ID) and subthreshold slope (SS) were analyzed.The model of the experimental omega-gate transistors was performed using the Look Up Table (LUT) method. The capacitance measurements of the nanowire transistor were also considered, to simulate the frequency responses more faithfully. The simulator used to design the OTA circuit was Cadence using the Verilog-A language. It was obtained the main figure of merit of this block like voltage gain (Av), gain-bandwidth product (GBW), phase margin and power.A transistor efficiency (gm/ID) near 8 V-1 was chosen in order to compare the performance of OTA designed with omega-gate nanowire devices (NW-OTA) of this work with anothers OTAs designed with triple gate FinFETs (FinFET-OTA) and with nanosheets (NS-OTA) from the literature (Table 1) [3,4].Table 1 shows that the phase margin is close to 60o in all cases, ensuring the stability of the circuit. The NW-OTA presents higher voltage gain compared to FinFET-OTA due to the better gate to channel coupling. The NS-OTA presents the highest voltage gain of all cases, but it is the more expensive technology [4]. When GBW is analyzed for all 3 designs, the NW-OTA shows better results than the NS-OTA, using the same load capacitance of 200fF, thanks to the lower miller capacitance (Cc) required to keep the frequency behavior. The FinFET-OTA shows the best result in relation to GBW, but the FinFET-OTA project doesn’t consider a load capacitance, making the comparison unfair [3].Figure 4 shows the gain and phase of the OTA using a SOI omega-gate nanowire transistors.In summary, the OTA designed with SOI omega-gate nanowire technology presents a better performance than FinFET one, can be implemented in a smaller area on the chip (smaller Cc capacitor and smaller number of fins in parallel) and it is a cheaper option compared to nanosheet one. Figure 1

A 0.8-Volt 29.52-μW Current Mirror-Based OTA Design for Biomedical Applications

An operational trans-conductance amplifier (OTA) is a fundamental component of electronic appliances. This paper introduces a novel design of OTA for minimal power, low voltage applications. The proposed OTA comprises an ultra low power current mirror design with enhanced bandwidth. The proposed OTA circuit is operated at 0.8[Formula: see text]V, contributing input noise of 26.33[Formula: see text]nV/(Hz)[Formula: see text] with a power of [Formula: see text]W. The additional parameters of new OTA are DC gain (87.32[Formula: see text]dB), common mode rejection ratio (145.47[Formula: see text]dB), gain bandwidth (4.73[Formula: see text]MHz), phase margin (36.56[Formula: see text]). These figures are significantly improved as compared to conventional OTAs. Analog-to-digital convertor (ADC) is also designed as an application of the proposed OTA. The improvements offered by ADC in terms of power and bandwidth are also compared with state of the art.

Realisation of low voltage low power class AB OTA and its application in biquadratic filter

ABSTRACT In this paper, a new high-performance Class AB operational transconductance amplifier circuit is introduced. Based on flipped voltage follower technique, the proposed OTA showed a high DC gain of 41.33 dB with a unity gain frequency at 14 MHz, a wide dynamic range, a total harmonic distortion of −42.61 dB at 100 kHz and occupies only 28.64 x 20.61 µm2 chip area. Thereafter, a new single-input-multi-output (SIMO) transadmittance mode filter possessed by three multi-output OTAs and two capacitors is realised. The proposed filter can be achieved by all the standard filter functions without changing the circuit topology. The post-layout simulation results of the proposed OTA and biquadratic filter have been implemented with Cadence Virtuoso in TS18SL 0.18 µm technology Tower Jazz.

MIOTA-Based Filters for Noise and Motion Artifact Reductions in Biosignal Acquisition

This paper presents a new low-voltage CMOS structure for operational transconductance amplifier (OTA) exploiting the bulk-driven, the self-cascode and the multiple-input transistor techniques (MI). The multiple-input OTA (MIOTA) circuit operates in subthreshold region using 0.5V supply voltage and offers enhanced linearity. The MIOTA is developed for biopotential signal as well as electrocardiogram (ECG) signal processing circuit and it is exploited to design a 5th-order Chebyshev low-pass and 3rd-order band-pass filters with a dynamic range (DR) of 57.6 dB and 60.4 dB, and nanopower consumption of 50 nW and 60 nW, respectively. Due to the electronic tuning of cut-off frequency, the low-pass and band-pass filters are suitable for random noise and motion artifact noise reductions in biopotential signals. The circuits were designed in Cadence environment using the standard N-well <inline-formula> <tex-math notation="LaTeX">$0.18~\mu \text{m}$ </tex-math></inline-formula> TSMC CMOS technology. Intensive post-layout simulation results along with the process, voltage, temperature analysis (PVT) and Monte Carlo (MC) prove the robustness of the design. The chip area of the proposed MIOTA is 0.00725 mm² (<inline-formula> <tex-math notation="LaTeX">$118~\mu \text{m}\,\,\times 61.5\,\,\mu \text{m}$ </tex-math></inline-formula>). Compared with standard OTA the MIOTA offers simplification of filter topology and reduced number of active elements. In order to demonstrate these advantages, the MIOTA-based filter was also build using commercially available OTA LT1228. The experimental results of OTA LT1228 confirm both the filter functionality and the advantages of the proposed MIOTA.

A 0.25-V Three-stage State Feedback Bulk-driven OTA for Wide Range Load Applications

This article employs a nested state feedback compensation technique to a three-stage bulk-driven operational transconductance amplifier (OTA). The projected OTA circuit consists of a bulk-driven PMOS amplifier, gate-driven NMOS amplifier, and common source (CS) amplifier. The entire transistors in the amplifier core are configuredwith self-cascode transistor topology to increase its output impedance. All transistors are designed to operate in a weak inversion in order to dissipate less power. Cross-coupled transistor pair topology in the bulk-driven stage allows to improve the effective transconductance of OTA. The CS amplifier can drive a large load capacitor. The polarities and transconductance gains of feedback blocks are controlled appropriately to obtain the desired DC gain and bandwidth. The capacitor-less compensation strategy allows the fabrication of the OTA using the minimum area. Conventional bulk-driven miler OTA, Bulk-driven stage improved indirect-feedback OTA (BSIF OTA), Gate-driven stage added bulk-driven OTA (GSIF OTA), and proposed bulk-driven OTA topologies are designed and simulated using cadence spectre tool at 25 mV supply voltage in the 65nm CMOS process. These OTA circuits are analyzed and compared in terms of parameters like DC gain, unity-gain frequency, phase margin, CMRR, power dissipated, slew rate, and input referred noise.

Power Efficient Biquadratic Filter designing using OTA

Objectives: To present a power efficient Universal Biquad Operational Transconductance Amplifier circuit. Methods: OTA (operational transconductance amplifier) based Biquad filter is analyzed using three different simulated tools three different tools (CADENCE, XILINX, ORCAD and MATLAB tools) are used for designing the circuit. The 0.18mm CMOS technique is used using the Cadence tool for plan and reproduction. The same circuit has been implemented on ORCAD tool as well as Xilinx tool. Findings: The proposed Biquad filter improves the frequency response, power dissipation and provides vary of the KHN biquadratic filter circuits it uses minimum numbers of Operational Transconductance phenomenon Amplifier (OTA) to realize an equivalent. The assorted parameters specifically Center frequency, dcgain, Bandwidth, Power Dissipation and Quality issue are all electronically tunable. OTA based Biquad filter is simulated in CADENCE Virtuoso tool. Opamp-RC Biquad filter offers a bandwidth of 425 kHz, pass band gain of zero DB, whereas Gm-C measuring system based mostly filter offers 85MHz, passband gain of zero DB. Over-all power dissipation of the Biquad filter is 4.3mW with 1.8V DC Supply has basing current of 50mA with gracefully voltage 2.5v. by keeping the supply voltage, bias current and load capacitor as 2.5V, 50mA and 10pFrespectively, it has been seen that the power is reduced using the CADENCE virtuoso tool. Novelty : This study presents a Universal Biquadratic filter having less power dissipation. The circuit was optimized for gain, GBP, slew rate, areas, voltage offset, phase margin, power area etc. compared to all the previous filter circuits (OTA GMC filters, OTA type-C filters) designed with the help of OTA. Keywords: OTA; CMOS; CADENCE Virtuoso; Static Power; Dynamic Power; MOSFET

Extended Bandwidth Method on Symmetrical Operational Transconductance Amplifier and Filter Application

In this paper, a symmetrical operational transconductance amplifier (OTA) circuit with extended bandwidth using resistive compensation technique is proposed. Into the all current mirrors of the symmetrical OTA circuit, this technique is applied. A passive resistor is connected between the gate and the drain of each primary transistor of the current mirrors in the symmetrical OTA structure. In addition, filter structures are realized in order to analyze the performance of the symmetrical OTA with extended bandwidth. Thus, the advantage of using resistive compensation technique is demonstrated. The symmetrical OTA with extended bandwidth and the filters are simulated with LTSPICE by using TSMC 0.18 μm CMOS process parameters.

Extended Bandwidth Method on Symmetrical Operational Transconductance Amplifier and Filter Application

In this paper, a symmetrical operational transconductance amplifier (OTA) circuit with extended bandwidth using resistive compensation technique is proposed. Into the all current mirrors of the symmetrical OTA circuit, this technique is applied. A passive resistor is connected between the gate and the drain of each primary transistor of the current mirrors in the symmetrical OTA structure. In addition, filter structures are realized in order to analyze the performance of the symmetrical OTA with extended bandwidth. Thus, the advantage of using resistive compensation technique is demonstrated. The symmetrical OTA with extended bandwidth and the filters are simulated with LTSPICE by using TSMC 0.18 μm CMOS process parameters.

Impact of gate current on the operational transconductance amplifier designed with nanowire TFETs

An Operational Transconductance Amplifier (OTA) designed with SiGe-source nanowire Tunnel-FETs is presented and compared with OTAs designed with Si nanowire (NW) TFETs and Si NW MOSFETs with and without the effect of gate current (IG). The devices were modeled using Verilog-A language through lookup tables obtained by experimental data and they were used to simulate the OTA circuits. It was observed that, when the IG is negligible, there is a trade-off between the DC open loop gain (AV0) and the gain-bandwidth product (GBW) of these circuits. The Si NW MOSFET OTA presented the lowest AV0 (52 dB) but the largest GBW (9.5 MHz). The largest gain was obtained by the Si NW TFET (97 dB) but it also presents the lowest GBW (30 kHz). The SiGe-source TFET stands in the middle, with an AV0 of 88 dB and a GBW of 715 kHz. However, when IG is not negligible and included in the model, the gain of the TFET OTAs decreases considerably, down to 38.3 dB in the case of the Si TFET and down to 52.6 dB in the case of the SiGe-source TFET. This decrease in gain is mostly caused by an alteration in the desired bias point in the second stage of the OTA due to the change of the output voltage and bias currents. This issue possibly can be mitigated by using circuit design strategies. Nevertheless, the SiGe-source TFET OTA is less impacted by the gate current than the Si TFET OTA and still presents a larger gain than the Si NW MOS OTA (52.6 dB against 50 dB) when the IG is considered.

Voltage gain improvement of the operational transconductance amplifier designed with silicon-on-insulator fin field effect transistor after being exposed to proton-irradiation

In this work, the influence of proton-irradiation in the voltage gain of two-stage operational transconductance amplifier (OTA) designed with silicon-on-insulator (SOI) fin field effect transistors (FinFETs) is studied. The OTA simulations were performed using Verilog-A approach based on experimental data extracted from the SOI FinFET electrical characterization, before and after proton-irradiation. The OTA is designed with SOI FinFETs of fin widths (W fin) of 20 nm, 120 nm, and 870 nm, all in the same predefined inversion region (g m/I D = 8 V−1). All evaluated OTA circuits exposed to proton-irradiation presented a voltage gain increase (compared with pre-irradiation circuits), of 0.87 dB, 1.19 dB, and 6.16 dB for fin widths of 20 nm, 120 nm, and 870 nm, respectively. The results show that despite the typical radiation effect of degradation of the individual transistors (it being more severe for larger fin width SOI FinFET), these effects combined in OTA circuits result in an unexpected improvement in DC voltage gain, especially for wider fins. Focusing on the fin width impact on the OTA voltage gain, before and after proton-irradiation, it is much greater for narrow fin width SOI FinFET thanks to the better Early voltage.

Design of FinFET Based Self-Biased OTA for Low Power Applications

This work explores the design of an Operational Trans conductance Amplifier (OTA) using Independent Gate (IG) FinFET. For the different configurations of FinFET such as IG, Low Power (LP) and Shorted Gate (SG), optimal gm and ro values have been found. FinFET devices are used to increase the performance by reducing the power dissipation as the front and back gate voltages are controlled independently. The designed three stage FinFET based OTA operates at 0.5 V power supply and achieves gain of 64 dB, 33 phase margin and 20 MHz unity gain frequency. The proposed OTA circuit is tested in Cadence virtuoso with FinFET 32nm BSIM-CMG model.

An ultra-low power high gain CMOS OTA for biomedical applications

An ultra-low power bulk-driven operational transconductance amplifier circuit for biomedical applications is presented. Higher DC gain and improved slew rate is achieved using double recycling technique, cross-coupled positive feedback configuration and driver transistors to enhance the transconductance of the conventional bulk-driven folded cascode amplifier. The post layout simulation of the proposed bulk-driven double recycling OTA in 180 nm CMOS technology, shows a 30 dB DC gain improvement and a 250% enhancement in GBW. The above results are validated using the Monte Carlo process variation and corner case simulations. The amplifier consumes 145 nW @ 0.6 V supply voltage.

Low Voltage Low Power Single Ended Operational Transconductance Amplifier for Low Frequency Applications

This paper presents the designing of a low voltage low power single ended operational transconductance amplifier (OTA) for low frequency application. The designed OTA combines three different schemes i.e. current splitting, current cancellation and source degeneration technique. Source degeneration method using resistor is one of the most simple and ubiquitous technique to linearize the transfer characteristics of OTA. Current splitting technique is utilized to reduce the transconductance of OTA and to improve the linearity. Current cancellation technique is used to further reduce the transconductance. The OTA circuit is operated in sub-threshold region due to the stringent power limitation requirement in integrated circuits. The transconductance of the OTA is 4.5 nA/V with a linear range of +/− 0.25 V. To test the applicability of the proposed OTA, a fifth order Butterworth OTA-C low pass filter is realized. The circuit is operated at a supply voltage of +/− 0.5 V and the power consumption of the filter is 487 nW. The DC gain of the filter is − 6.1 dB with a cutoff frequency of 250 Hz. THD of − 50.61 dB of the OTA-C filter is obtained for a 100 mVpp signal with 100 Hz frequency. The circuit shows the best THD performance with less pass band attenuation for single ended filter circuit. The circuit is simulated in cadence environment using 150 nm CMOS process technology.

Realization of current-mode biquadratic filter employing multiple output OTAs and MO-CCII

This paper presents a low voltage low power operational transconductance amplifier circuit. By using a source degeneration technique, the proposed realization powered at ±0.9V shows a high DC gain of 63dB with a unity gain frequency at 3.5MHz, a wide dynamic range and a total harmonic distortion of −60dB at 1MHz for an input of 1Vpp. According to the connection of negative current terminal to positive voltage terminal of double output OTA circuit, a second generation current conveyor (CCII-) has been realized. This circuit offers a good linearity over the dynamic range, an excellent accuracy and wide current mode of 56MHz and voltage mode of 16.78MHz cut-off frequency f-3dB.Thereafter, new SIMO current-mode biquadratic filter composed by OTA and CCII as active elements and two grounded capacitors is implemented. This filter is characterized by (i) independent adjusting of pole frequency and quality factor, (ii) it can realize all simulations results without changing the circuit topology, (iii) it shows low power consumption about 0.24mW. All simulations are performed by Cadence (Cadence Design Systems) technology Tower Jazz 0.18μm TS18SL.

FinFET Based Tunable Analog Circuit: Design and Analysis at 45 nm Technology

We included a designing of low power tunable analog circuits built using independently driven FinFETs devices, where the controlling of the back gate provide the output on the front gate. We show that this could be an effective solution to conveniently tune the output of bulk CMOS analog circuits particularly for Schmitt trigger and operational transconductance amplifier circuits. FinFET devices can be used to increase the performance by reducing the leakage current and power dissipation, because front and back gates both are independently controlled. FinFET device has a higher controllability, resulting relatively high Ion/Ioff ratio. In this paper, we proposed a tunable analog circuit such as CMOS amplifier circuit, Schmitt trigger circuit, and operational transconductance amplifier circuit, these circuit blocks are necessary for low noise high performance ICs for analog applications. Gain, phase, group delay, and output response of analog tunable circuits have been discussed in this paper. The proposed FinFET based analog tunable circuits have been designed using Cadence Virtuoso tool at 45 nm.

A Novel Design Method of Two-Stage CMOS Operational Transconductance Amplifier used for Wireless Sensor Receiver

Operational transconductance amplifier (OTA) is one of the most significant building-blocks in integrated discret-time filters used in analog to digital converter (ADC) for Sigmadelta converter. In this paper we designed a novel design method of two-stage CMOS amplifier in AMS 0.35μm technology. P-Spice simulation results confirm the proposed OTA circuit. In fact, we achieved a gain band width (GBW) equal to 55 MHz, Cut-off frequency of 85 KHz and 57 dB gain (Av). In addition our new method allowed us to reduce settling time (St) to 15.6 ns and a slew rate (SR) of 0.1 V/μs at ±1.5V supply voltage. Eventually we have also succeeded in reducing the average power consumption to 1.65 mW while driving 3 pF load capacitor. General Terms Microelectronic Components Circuits Devices & Systems

Low power current sources for bioimpedance measurements: a comparison between Howland and OTA-based CMOS circuits

Abstract Multifrequency Electrical Bioimpedance (MEB) has been widely used as a non-invasive technique for characterizing tissues. Most MEB systems use wideband current sources for injecting current and instrumentation amplifiers for measuring the resultant potential difference. To be viable current sources should have intrinsically high output impedance for a very wide frequency range. Most contemporary current sources in MEB systems are based on the Howland circuit. The objective of this work is to compare the Mirrored Modified Howland Current Source (MMHCS) with three Operational Transconductance Amplifier (OTA) based voltage controlled current sources (i.e., class-A, class-AB and current conveyor). The results show that both current conveyor and class-AB OTA-based current sources have a wider output current frequency response and an output impedance of 226% larger than the MMHCS circuit at 1 MHz. The presented class-AB OTA circuit has a power consumption of 4.6 mW whereas current conveyor consumed 1.6 mW. However, the MMHCS circuit had a maximum total harmonic distortion of 0.5% over the input voltage from -0.5 to +0.5 V. The OTA-based current sources are going to be integrated in a semiconductor process. The results might be useful for cell impedance measurements and for very low power bioimpedance applications.

Programmable feedforward linearized CMOS OTA for fully differential continuous‐time filter design

AbstractIn this paper, a feedforward linearization method for programmable CMOS operational transconductance amplifier (OTA) is described. The proposed circuit technique is developed using simple source‐coupled differential pair transconductors, a feedback‐loop amplifier for self‐adjusting transcoductance (gm) and a linear reference resistor (R). As a result, an efficient linearization of a transfer characteristic of the OTA is obtained. SPICE simulations show that for 0.35µm AMS CMOS process with a single +3V power supply, total harmonic distortion at 1 Vpp and temperature range from −30 to +90°C is less than −49.3 dB in comparison with −35.8 dB without linearization. Moreover, the input voltage range of linear operation is increased. Power consumption of the linearized OTA circuit is 0.86 mW. Finally, the OTA is used to design a third‐order elliptic low‐pass filter in high‐frequency range. The cut‐off frequency of the operational transconductance amplifier‐capacitor (OTA‐C) filter is tunable in the range of 322.6 kHz–10 MHz using the feedforward linearized OTAs with the digitally programmable current mirrors. Copyright © 2009 John Wiley &amp; Sons, Ltd.