Carbon Nanotube Field Effect Transistor Technology Research Articles

Low-power and robust ternary SRAM cell with improved noise margin in CNTFET technology

In this paper, a carbon nanotube field-effect transistor (CNTFET) based low power and robust ternary SRAM (TSRAM) cell with enhanced static noise margin (SNM) has been proposed. The proposed cell uses a low-power cell core and a stack of 2 CNTFETs to discharge the read bit line (RBL) to ground, unlike the previous SRAM designs which use read buffers or transmission gates (TG) to alter the voltage levels on the RBL. The proposed TSRAM cell has been simulated relentlessly, using the Stanford 32 nm CNTFET technology mode file with Synopsis HSPICE tool under various operating conditions. Unlike other designs, the cross-coupled ternary inverters used as the cell core in the proposed TSRAM show higher gain and steep curves in the transition region mitigating the static power of the cell. The simulation results exhibit improvements in performance parameters like power consumption, energy, noise margins, and reliability. At 0.9 V supply voltage, the proposed TSRAM cell offers 52.44% and 43.17% reduction in write and read static power, a PDP reduction of 35.29% in comparison, and a 36.36% improvement in SNM compared to the best designs under investigation. Also, the proposed TSRAM design shows higher robustness compared to other designs.

Enhancing high-speed digital systems: MVL circuit design with CNTFET and RRAM

Multiple Value Logic (MVL) circuits in high-speed digital systems can represent significantly more information than traditional binary logic circuits. The increasing demand for enhanced data storage capacity has driven the adoption of MVL circuits. However, designing MVL circuits presents challenges, particularly in achieving improved performance aligned with the desired threshold voltage. To address this challenge, harnessing carbon nanotube field-effect transistors (CNTFETs) has been instrumental in designing MVL circuits. CNTFETs offer distinct advantages due to their large resistors. Furthermore, substituting these resistors with Resistive Random Access Memory (RRAM) to implement Ternary logic circuits enhances storage capacity by enabling multiple resistance states within a single cell. This paper presents a novel MVL circuit design that leverages the unique characteristics of CNTFETs and RRAM. Additionally, gate implementation is explored using a Recurrent Neural Network − Long-Short Term Memory (RNN-LSTM) based Tasmanian Devil Optimization algorithm. The practical implementation uses Synopsis HSPICE software with CNTFET technology at 32 nm. A comprehensive performance analysis compares this approach with state-of-the-art solutions regarding delay, area, and power consumption. Significant reductions in area, power consumption, and transistor count are revealed with the proposed approach.

CNTFET-based SRAM cell design using INDEP technique

As the size of the transistor decreases in the nanoscale regime, certain parameters, such as, cell stability, power dissipation, and delay, have changed. This poses a significant challenge when attempting to scale down metal oxide semiconductor field effect transistor (MOSFET). The carbon nanotube field effect transistor (CNTFET) has exhibited remarkable advantages compared to MOSFETs in circuit designs within the nanoscale range, owing to its extraordinary characteristics. In this work, a CNTFET-based six-transistor (6T) static random access memory (SRAM) cell is designed using the low power input-dependent (INDEP) technique. The suggested circuits' performance and efficiency is enhanced using CNTFET technology. The suggested design undergoes circuit simulations using the 32 nm CNTFET Stanford model. The results obtained from the simulations indicate that the suggested INDEP 6T SRAM cell surpasses both the conventional 6T SRAM cell and the previous designs in terms of power dissipation, delay, and energy efficiency. The hold, read, and write operations use less power, and the hold and write operations take less time to complete. The suggested design also demonstrates improved energy efficiency for hold and read operations compared to the conventional design. Furthermore, a stability analysis is conducted on the suggested INDEP 6T SRAM cell using the static noise margin (SNM) metric. The suggested INDEP approach in comparison to the other schemes has greater SNMs for hold, write, and read operations, indicating improved SRAM cell stability.

CNTFET and RRAM Based Low Power Design of Unbalanced Ternary Logic Gates and Arithmetic Circuits

The advent of multi-valued logic (MVL) systems provides considerable improvements in energy consumption and computational efficiency compared to binary logic systems. Using resistive random-access memory (RRAM) and carbon nanotube field effect transistors (CNTFETs), this manuscript presents a new design method for ternary logic gates (standard ternary inverter (STI), ternary NOR, and ternary NAND) and some arithmetic circuit applications are implemented based on the proposed ternary logic gates. The simulations of the proposed circuits are carried out in Synopsis HSPICE software by employing 32-nm Stanford CNTFET technology along with the Stanford RRAM model. The robustness of the designed CNTFET-RRAM STI circuit is investigated for variations in process parameters. Simulation results verify that the proposed designs outperform other CNTFET based ternary logic circuits in terms of number of components, power consumption, delay and power delay product (PDP). Furthermore, a reduced change is perceived with respect to power consumption and PDP of the presented logic gates with process deviation, and variations in supply voltage, temperature, capacitance and frequency. The presented STI, TNAND, TNOR, ternary half adder (THA) and ternary multiplier (TMUL) circuits exhibit an improvement in PDP with less transistor count as compared to the other existing designs in the literature.

A low-power high speed full adder cell using carbon nanotube field effect transistors

The adder circuit is basic component of arithmetic logic design and that is the most important block of processor architecture. Moreover, power consumption is the main concern for real-time digital systems. In recent times, carbon nanotube field effect transistors (CNTFET) used for arithmetic circuit designs with high performance. A creative substitute for highspeed, less power, and small size in area designs is the CNTFET. This paper presents 1- bit full adder with CNTFETs for low power and high performance. Using the computer aided design (CAD) tool the proposed 1-bit full adder design model is simulated using 32 nm with CNTFET technology, a voltage supply of +0.9V. Performance comparisons between various proposed designs and existing 1-bit full adder design have been made in terms of the delay, power, and power delay product (PDP). The proposed CNFET logic also design for n-bit carry look adder (CLA) and compare it to other CLAs to evaluate performance and reliability. The simulation results shows that the proposed adder consume less power than existing adders.

Stability and Power Analysis of Schmitt Trigger Based Low Power SRAM Bit-Cell Using CMOS and CNTFET Technology at 22nm Technology Node

SRAM (Static Random Access Memory) is an essential component of memory devices such as laptops, phones, etc., which act as a semiconductor memory. The “Carbon Nanotube Field Effect Transistor (CNTFET)” is silicon associated high-stability, low-power device with excellent performance. CNTFET has been verified to be very advantageous for Very large-scale integration circuit designs in the nanoscale range because of its remarkable properties of metal oxide semiconductor field effect transistor (MOSFET). The material was brought to light because of its genuinely incredible electrochemical performance. Carbon nanotubes have unique properties such as high charge carrier mobility, high voltage, small footprint, exceptionally short and high control over pulse duration, and large current densities. In traditional MOSFET, bulk silicon is used, which has high leakage current and high field-effect; thus, CNTFET has been used as an alternative in recent years. When compared to the 10T CNTFET SRAM Bit cell is designed using HSPICE Tool in 22nm technology. Long-term stability and significant process variable changes are significant challenges with nanoscale SRAM cells.

A High-Speed Low-Energy One-Trit Ternary Multiplier Circuit Design in CNTFET Technology

Contemporary system-on-chip-based applications are battery-powered. To increase the operation time, they need various low-power/energy circuits. Carbon nanotube field-effect transistor (CNTFET) is a potential alternative to complementary metal-oxide-semiconductor for power/energy-efficient circuits implementation due to offering high performance. Another way to reduce power/energy consumption in a circuit is to use multiple-valued logic, especially ternary logic, which has three logical states. This paper presents a novel 1-trit ternary multiplier circuit with 23 transistors based on only unary operators of the ternary logic system and the dual-supply voltages technique. The proposed design does not use the ternary decoder/encoder, logic gates, cascading transmission gates, and ternary multiplexer to reduce the transistors count, delay, power, and energy. The Stanford CNTFET model in the 32 nm technology node is used to simulate the proposed design. The delay, power, and delay-power-product (PDP) of the proposed design at 0.9 V are 0.026 ns, 0.139 μW, and 3.614 aJ, respectively. It offers improvements between 50% and 61.19% in delay and between 52.72% and 59.75% in PDP compared to previously published multiplier circuits, which are based on the dual-supply voltages and use 23 transistors. These improvements make the proposed design a good candidate for the design of the next generation of multiplier circuits in arithmetic blocks.

Design and analysis of ternary delay flip-flop implemented with carbon nanotube field effect transistor

Flip-flops serve as fundamental memory storage elements in digital circuits, and their efficiency significantly affects overall circuit performance. The aim of this study is to create a D flip-flop based on ternary logic and evaluate its performance in comparison to flip-flops that have already been designed. The proposed D flip-flop design leverages Carbon Nanotube Field Effect Transistors (CNTFETs). CNTFETs offer unique properties that can enhance the speed and power efficiency of flip-flop design. To evaluate the performance of the proposed design, it was simulated using the HSPICE simulator with a 32 nm Stanford CNTFET model. The simulation parameters include a power supply voltage of 0.9 volts and an operating frequency of 1 GHz. These specific settings allow researchers to analyze the behavior and performance of flip-flops under realistic operating conditions. By comparing the simulation results of the proposed D flipflop with the performance of previously designed flip-flops, the improvements are assessed in terms of the speed and power consumption. The simulation results provide valuable insights into the efficiency, reliability, and responsiveness of the proposed design. The findings of this research contribute to the advancement of digital circuit design by introducing a novel D flip-flop based on ternary logic and CNTFET technology. The goal is to enhance the overall performance efficiency of digital circuits, particularly in applications where D flip-flops are used as building blocks such as shift registers.

Arithmetic Logic Unit Circuit Designed for Near-Sensor Computing Architecture With Complementary Carbon Nanotube Field-Effect Transistor Technology

Arithmetic Logic Unit Circuit Designed for Near-Sensor Computing Architecture With Complementary Carbon Nanotube Field-Effect Transistor Technology

An SEU-hardened ternary SRAM design based on efficient ternary C-elements using CNTFET technology

Ternary logic has been investigated for several years as it can provide substantial advantages in reducing the complexity of operations and the number of interconnects. On the other hand, with the advancement of technology and the reduction of the feature size and supply voltage, the sensitivity of memory elements to radiation effects has increased. In this paper, a robust ternary SRAM (TSRAM) cell is designed using a novel ternary C-element based on carbon nanotube field-effect transistors (CNTFETs). Besides, a 2m×2n ternary memory array architecture is designed and simulated based on the proposed TSRAM cell. Unlike the previous TSRAM cells, our proposed cell is hardened against radiation effects caused by high-energy particle strikes, which is a significant achievement in ternary memory design. Our extensive simulations demonstrate that the proposed radiation-hardened TSRAM offers up to 77× higher critical charge and up to 98 % higher SNM at the cost of 47 % to 65 % area overhead. It is also noteworthy that the proposed design only needs only two threshold voltages. Moreover, the proposed TSRAM is robust against the process and temperature variations. Our results emphasize that the proposed design is a milestone for designing high-performance, radiation-hardened, and robust ternary memory chips.

Voltage over‐scaling CNT‐based 8‐bit multiplier by high‐efficient GDI‐based counters

A new low-power and high-speed multiplier is presented based on the voltage over scaling (VOS) technique and new 5:3 and 7:3 counter cells. The VOS reduces power consumption in digital circuits, but different voltage levels of the VOS increase the delay in different stages of a multiplier. Hence, the proposed counters are implemented by the gate-diffusion input technique to solve the speed limitation of the VOS-based circuits. The proposed GDI-based 5:3 and 7:3 counters save power and reduce the area by 2x and 2.5x, respectively. To prevent the threshold voltage (Vth) drop in the suggested GDI-based circuits, carbon nanotube field-effect transistor (CNTFET) technology is used. In the counters, the chirality vector and tubes of the CNTFETs are properly adjusted to attain full-swing outputs with high driving capability. Also, their validation against heat distribution under different time intervals, as a major issue in the CNTFET technology is investigated, and their very low sensitivity is confirmed. The low complexity, high stability and efficient performance of the presented counter cells introduce the proposed VOS-CNTFET-GDI-based multiplier as an alternative to the previous designs.

Low leakage, differential read scheme CNTFET based 9T SRAM cells for Low Power applications

ABSTRACT Electronic devices are persisting as the integral part in various medical devices. These devices require SRAMs (Static Random Access Memory) with power efficient capability to handle the data, as they occupy most of the die area. Especially, wearable devices are bringing new challenges in the design of an IC, where high stability and low static power dissipation are very much required. In this paper, two new Carbon Nanotube Field Effect Transistor (CNTFET) based 9T SRAM cell topologies are presented to improve the leakage power dissipation at standby mode while maintaining the stability of the cell. Differential bitlines with decoupled read port are used to assist the read disturbance and the subthreshold lowering as well as stack of transistors are employed to curtail the leakage power. The circuits are implemented at 900 mv in Cadence using CNTFET technology. The Architecture with a 4 × 4 array matrix of the proposed 9T cells is designed. These are found to be the better ones yielding good results compared to the existing designs.

Performance Optimization of Carbon Nano-Tube Field Effect Transistors by Tuning Parameters

As transistors are scaled down to keep up with Moore's law, the semiconductor industry is facing several challenges due to the limitation of traditional Metal Oxide Semiconductor Field Effect Transistor (MOSFET) technology. To overcome this issue of scalability, various other technologies are being researched. Among them are Carbon Nano-Tube Field Effect Transistors (CNTFET), Ribbon Field Effect Transistors (RibbonFET), Graphene Nanoribbon Field Effect Transistor (GNRFET), and Fin shaped Field Effect Transistor (FinFET), which can substitute MOSFETs. Due to carbon nanotubes' excellent conductivity supremacy, CNTFETs are a promising new solution. However, implementing a CNTFET and making circuits from it is still challenging as CNTFETs can exhibit properties of both semiconductor and metal depending on various parameters. This paper will illustrate the characteristics of the CNTFET, compare the power consumption and propagation delay of basic logic gates made using the CNTFET and MOSFET technology. The parameter tuning is done by measuring the power and delay for all parameter values. The Simulation of CNTFET is done on the Stanford CNTFET model using H-Spice.

Implementation and Optimization of CNTFET Based Ultra-Low Energy Delay Flip Flop Designs

Energy conservation and delay minimization are the two major goals while designing ultra-low-power digital integrated circuits at lower technology nodes. Here, silicon based carbon nanotube field effect transistor (CNTFET) has been explored as a novel material for future electronics design applications (EDA). In this paper, two energy-efficient switching activity minimization techniques have been applied with proposed designs. First technique detects the completion of sensing stage operation known as transition completion detection (TCD) technique. TC signal generated from NAND operation of complementary outputs of sensing stage which minimizes glitches in the complementary outputs of the latch stage. Another clock gating mechanism applied at the latch stage to smoothen the output waveforms Q and \(\overline {Q}\). The proposed and existing designs simulated using 32nm CMOS and 32nm CNTFET technology, indicating that the CNTFET based design reduces power by 45% and 36% respectively in comparison with conventional CMOS. Proposed Low Power Sense Amplifier Flip Flop with transition control detection (TCD-LPSAFF) and Ultra Low Energy Sense Amplifier Flip Flop (ULESAFF) give minimal power delay product (PDP) which is 35.7 × 10− 18 J and 29.6 × 10− 18 J respectively. Also, the effect of process variation has been analyzed at specified corners (FF, TT and SS) in the temperature range of -40∘C to 120 ∘C. The performance of all designs has been validated by functionality testing with variation in load cpacitance, diameter, number of tubes and pitch respectively.

Energy Efficient Tri-State CNFET Ternary Logic Gates

Power consumption and especially leakage power are the main concerns of nano MOSFET technology. On the other hand, binary circuits face a huge number of interconnection wires, which results in power dissipation and area. Researchers introduced emerging nanodevices and multiple-valued logic (MVL) as two feasible solutions to overcome the challenges mentioned above. Carbon nanotube field-effect transistor (CNFET) is one of the emerging technologies that has some unique properties and advantages over MOSFET, such as adjusting the carbon nanotube (CNT) diameters to have the desired threshold voltage and have the same mobility as P-FET and N-FET transistors. In this paper, we present a novel method for designing ternary logic circuits based on CNFETs. Each of our designed logic circuits implements a logic function and its complementary via a control signal. Also, these circuits have a high impedance state, which saves power while the circuits are not in use. Moreover, we designed a two-digit adder/ subtractor and a power-efficient ternary logic arithmetic logic unit (ALU) based on the proposed gates. The proposed ternary circuits are simulated using HSPICE via standard 32 nm CNFET technology. The simulation results indicate the designs’ correct operation under different process, voltage, and temperature (PVT) variations. Also, simulation results show that the two-digit adder/ subtractor using our proposed gates has 12X and 5X lower power consumption and power-delay product (PDP), respectively, compared to previous designs.

Design of high stability, low power and high speed 12 T SRAM cell in 32-nm CNTFET technology

Many researchers are trying to create a low power, high stability, and high-speed static random access memory (SRAM) cell. This paper introduces an SRAM cell consisting of 12 transistors (12 T) developed by carbon nanotube field-effect transistor (CNTFET) to support such an endeavor and be a milestone in creating a better SRAM cell. The proposed 12 T CNTFET SRAM cell is a modified Schmitt-trigger (ST)-based SRAM cell design. The ST-based SRAM cell feedback-cutting and single-ended read decupled techniques are introduced to improve the SRAM cell’s static noise margin (SNM) and access time. The presence of stacked N-CNTFETs reduces the proposed cell’s power consumption. In addition to conventional 6 T [9] and 8 T [10] SRAM cells, it has been compared with some of the existing SRAM cells such as 12 T SRAM [11], 12 T SRAM [12], 12 T SRAM [13] and 12 T SRAM [14], for calculating the relative performance of the proposed 12 T CNTFET SRAM cell design in terms of fundamental design metrics. The simulation results at 0.9 V show that compared to the afromentioned bit cells, the proposed design accomplishes low power consumption while writing, reading, and holding modes of operation. It has a high SNM during all the operations. The proposed cell has the least read access time. The power, SNM, and access time performance of the bit cells are evaluated for the variation of CNTFET parameters and reported in this article. The proposed cell is also implemented using MOSFET, and the performance of MOSFET and CNTFET is compared. The simulation is done with the HSPICE simulation tool using the Stanford University 32 nm CNTFET model.

Design of High Stability and Low Power 7T SRAM Cell in 32-NM CNTFET Technology

A novel 7T carbon nanotube field effect transistor (CNTFET)-based static random-access memory (SRAM) cell is proposed in this paper. Power and noise margin performances of the proposed SRAM cell is observed for write, hold and read operations. The power consumption and noise margin of the proposed SRAM cell is compared with the conventional 6T and 8T CNTFET-based SRAM cells. From the simulation, it is noted that the proposed 7T SRAM cell consumes lesser power and offers high static noise margin (SNM) compared to that of conventional 6T and 8T SRAM cells. The introduction of diode-based transistor structure improves the power and noise performance of the proposed SRAM cell. The effect of variation of parameters such as gate oxide thickness, dielectric constant, pitch, temperature, number of carbon nanotubes (CNT) and supply voltage on power and noise performance of proposed 7T SRAM cell is studied. Simulations were carried out with HSPICE simulation tool using Stanford University 32-nm CNTFET model.

A new low-power Dynamic-GDI full adder in CNFET technology

In this paper, a new low-power full-adder circuit based on the proper combination of dynamic logic style and Gate Diffusion Input (GDI) low-power technique is proposed in Carbon Nanotube Field Effect Transistor (CNFET) technology. Using the proposed approach, the basic logic circuits such as XOR and XNOR gates are implemented which results in a full-swing, full-adder cell in the CNFET technology. The proposed circuit is simulated in HSPICE using CNFET model parameters. Finally, the simulation results justify a good improvement in the major circuit performances such as power consumption, delay and power-delay product (PDP) parameters for the proposed full-adder circuit.

Design and Analysis of Low-Power and High Speed Approximate Adders Using CNFETs.

Adders are constituted as the fundamental blocks of arithmetic circuits and are considered important for computation devices. Approximate computing has become a popular and developing area, promising to provide energy-efficient circuits with low power and high performance. In this paper, 10T approximate adder (AA) and 13T approximate adder (AA) designs using carbon nanotube field-effect transistor (CNFET) technology are presented. The simulation for the proposed 10T approximate adder and 13T approximate adder designs were carried out using the HSPICE tool with 32 nm CNFET technology. The metrics, such as average power, power-delay product (PDP), energy delay product (EDP) and propagation delay, were carried out through the HSPICE tool and compared to the existing circuit designs. The supply voltage Vdd provided for the proposed circuit designs was 0.9 V. The results indicated that among the existing full adders and approximate adders found in the review of adders, the proposed circuits consumed less PDP and minimum power with more accuracy.

Design and analysis of energy‐efficient compressors based on low‐power XOR gates in carbon nanotube technology

Compressors are the fundamental components in multipliers to accumulate and reduce partial product stages in a parallel manner. This study presents several architectures for low-power 4-2 and 5-2 compressors, which are based on the proposed circuits of the full-swing and non-full-swing XOR gates in carbon nanotube field effect transistor (CNTFET) technology. The CNTFET technology has been chosen because of its unique electrical and mechanical features. The proposed circuits are investigated in terms of process, voltage and temperature variations, delay, power dissipation, energy, power-delay product (PDP) and transistor count. All the proposed and referenced designs are simulated using an HSPICE tool in a 32 nm CNTFET Stanford technology model. The results show that the proposed circuits have less PDP and power consumption than the previous work. The proposed compressors have the lowest PDP, achieving 5.8%–41.9% improvement.