Capacitive Threshold Logic Research Articles

21T Ternary Full Adder based on Capacitive Threshold Logic and Carbon Nanotube FETs

21T Ternary Full Adder based on Capacitive Threshold Logic and Carbon Nanotube FETs

A Novel Efficient CNFET-Based Inexact Full Adder Design for Image Processing Applications

Employing inexact arithmetic circuits in error-resilient applications results in reduction of hardware-level metrics such as power consumption, delay and occupied area. These criteria are very important in portable applications because they are battery limited. Full Adder cell is as a building block of many arithmetic circuits. Therefore, it can influence the performance of the entire digital system. This paper presents a novel low-power and high-speed design of one-bit inexact full adder cell based on 32-nm (CNFET) technology for error resilient applications. This design technique can be utilized in various applications particularly in image processing. The presented design employs capacitive threshold logic (CTL) approach which significantly reduces the number of transistors. The peak signal-to-noise ratio (PSNR) is considered to evaluate accuracy of circuits at application level. Then extensive simulations regarding various power supplies, temperatures and loads at transistor level are performed to measure power consumption and propagation delay criteria. Moreover, some new metrics are introduced to trade-off between application and hardware level parameters. Comprehensive simulations demonstrate the supremacy of the proposed cell than others.

Design of efficient approximate 1-bit Full Adder cells using CNFET technology applicable in motion detector systems

In this paper, we present two novel approximate Full Adder cells with capacitive threshold logic (CTL) using carbon nanotube field-effect transistor (CNFET) technology. To investigate the efficiency of the proposed cells, extensive simulations are carried out at both application and transistor levels. At the application level, by using the MATLAB tool, the proposed cells are applied to the motion detector algorithm as one of the practical image processing applications. Peak signal-to-noise ratio (PSNR) is considered as a legitimate application-level evaluating factor. In addition, by using the HSPICE tool, the hardware level parameters such as average power consumption, delay, and power-delay product (PDP) are estimated. Then, a compromise between the application and hardware-level metrics is considered. Noise analysis is also accomplished by taking noise immunity curve (NIC) and average noise threshold energy (ANTE) into account. Furthermore, Monte Carlo transient analysis is exploited to study the robustness of the introduced cells against diameter deviations of the carbon nanotubes (CNTs). Simulation results indicate the supremacy of the proposed cells compared to others.

High‐speed energy efficient process, voltage and temperature tolerant hybrid multi‐threshold 4:2 compressor design in CNFET technology

Compressors are fundamental components in multi-operand addition and multiplication hardware. The present study aims to propose several high-speed hybrid designs of 4:2 compressors which are implemented based on multi-threshold logic and transmission gate multiplexers, at low supply voltages. In order to implement these circuits, carbon nanotube field-effect transistors (CNFETs) are utilised. The division of the entire input capacitor network in the third proposed design causes the entire structure operates faster and consumes less power. All designs were simulated with Synopsys HSPICE and 32 nm CNFET technology in different conditions. Simulation results demonstrate the superiority of the third proposed design with regard to different load and frequency conditions. In addition, it becomes less sensitive to process, voltage and temperature variations compared to other similar capacitive threshold logic circuits. The results indicate the third proposed design outperforms the best reference design in terms of delay and power-delay product by 34 and 25%, respectively. Furthermore, the performance of each design was evaluated in a 8 × 8-bit binary multiplier as a uniform test bench, which confirmed the above results on isolated single 4:2 compressors.

A low-PDAP and high-PSNR approximate 4:2 compressor cell in CNFET technology

PurposeThis paper aims to present an inexact 4:2 compressor cell using carbon nanotube filed effect transistors (CNFETs).Design/methodology/approachTo design this cell, the capacitive threshold logic (CTL) has been used.FindingsTo evaluate the proposed cell, comprehensive simulations are carried out at two levels of the circuit and image processing. At the circuit level, the HSPICE software has been used and the power consumption, delay, and power-delay product are calculated. Also, the power-delaytransistor count product (PDAP) is used to make a compromise between all metrics. On the other hand, the Monte Carlo analysis has been used to scrutinize the robustness of the proposed cell against the variations in the manufacturing process. The results of simulations at this level of abstraction indicate the superiority of the proposed cell to other circuits. At the application level, the MATLAB software is also used to evaluate the peak signal-to-noise ratio (PSNR) figure of merit. At this level, the two primary images are multiplied by a multiplier circuit consisting of 4:2 compressors. The results of this simulation also show the superiority of the proposed cell to others.Originality/valueThis cell significantly reduces the number of transistors and only consists of NOT gates.

An efficient inexact Full Adder cell design in CNFET technology with high-PSNR for image processing

ABSTRACTThe design of inexact circuits at the transistor level remarkably improves figures of merits such as power consumption, delay, energy, and area. Therefore, inexact technique for designing circuits has attracted the attention of researchers worldwide. Designing inexact Full Adder cell as a building block of a variety of arithmetic circuits can affect the entire electronic system’s performance. In this paper, two novel inexact 1-bit Full Adder cells are presented using carbon nanotube field effect transistors (CNFETs). The capacitive threshold logic (CTL) is used to realize the proposed cells. Comprehensive simulations at two levels of abstraction, i.e., application and hardware are carried out to evaluate the efficacy of these circuits. First, the motion detector which is one of the image processing applications is deployed in MATLAB software to measure peak signal-to-noise ratio (PSNR) figure of merit. At hardware level, the HSPICE tool is used to carry out simulations and measure power, delay, power-delay product (PDP), energy-delay product (EDP), power-delay-area product (PDAP) and power-delay-area-PSNR product (PDAPP). Simulation results confirmed the superiority of the proposed Full Adder cells compared to others. For instance, the proposed 6TIFA improves PDAPP metric at least 21% and at most 76% compared to its counterparts at 0.9V power supply.

High-Performance Ternary (4:2) Compressor Based on Capacitive Threshold Logic

Abstract This paper presents a ternary (4:2) compressor, which is an important component in multiplication. However, the structure differs from the binary counterpart since the ternary model does not require carry signals. The method of capacitive threshold logic (CTL) is used to achieve the output signals directly. Unlike the previously presented similar structure, the entire capacitor network is divided into two parts. This segregation results in higher reliability and robustness against unwanted process, voltage, and temperature (PVT) variations. Simulations are performed by HSPICE and 32nm CNFET technology. Simulation results demonstrate about 94% higher performance in terms of power-delay product (PDP) for the new design over the previous one.

A capacitive multi-threshold threshold gate design to reach a high-performance PVT-tolerant 4:2 compressor by carbon nanotube FETs

This paper presents two new 4:2 compressors based on capacitive multi-threshold threshold logic (MTTG), and Carbon Nanotube Field Effect Transistors (CNFETs). The entire capacitor network is divided into two groups in one of the proposed designs. As a result, the number of voltage levels is reduced and the entire structure becomes less sensitive to Process, Voltage, and Temperature variations in comparison with other similar capacitive Threshold Logic (TL) circuits. All designs are simulated by Synopsys HSPICE and 32 nm CNFET technology in different situations and conditions. Simulation results demonstrate the superiority of the second proposed design. It operates 55.9% faster and consumes about 7.2% less power than the second best TL structure (CSTFA). It also operates 16.2% faster and consumes 13.6% less energy in comparison with a traditional design (BLG). Moreover, estimations show that the first proposed design occupies the least area among the capacitive TL circuits.

Realisation of multiple-valued functions using the capacitive threshold logic gate

The circuit-level hardware realisation of several multiple-valued logic functions using the capacitive threshold logic design style is presented. The generic design approach for multiple-input, multiple-output and multiple-level transfer functions is shown. SPICE simulations of complex operators demonstrate correct operation which qualifies the proposed circuits for integration into larger multiple-valued logic systems. An analysis of noise margin figures and comparisons with previously published circuit examples are provided.

A Modular and Scalable Architecture for the Realization of High-speed Programmable Rank Order Filters Using Threshold Logic

We present a new scalable architecture for the realization of fully programmable rank order filters (ROF). Capacitive Threshold Logic (CTL) gates are utilized for the implementation of the multi-input programmable majority (voting) functions required in the architecture. The CTL-based realization of the majority gates used in the ROF architecture allows the filter rank as well as the window size to be user-programmable, using a much smaller silicon area, compared to conventional realizations of digital median filters. The proposed filter architecture is completely modular and scalable, and the circuit complexity grows only linearly with maximum window size (m) and with word length (n). A prototype of the proposed filter circuit has been designed and fabricated using double-polysilicon 0.8 μm CMOS technology. Detailed post-layout simulations and test results of the ROF prototype circuit indicate that the new architecture can accommodate sampling clock rates of up to 50 MHz, corresponding to an effective data processing rate of 800 Mb/s for a very large filter with window size 63 and word length of 16 bits.

A compact high-speed (31,5) parallel counter circuit based on capacitive threshold-logic gates

A novel high-speed circuit implementation of the (31,5)-parallel counter (i.e., population counter) based on capacitive threshold logic (CTL) is presented. The circuit consists of 20 threshold logic gates arranged in two stages, i.e., the parallel counter described here has an effective logic depth of two. The charge-based CTL gates are essentially dynamic circuits which require a periodic refresh or precharge cycle, but unlike conventional dynamic CMOS gates, the circuit can be operated in synchronous as well as in asynchronous mode. The counter circuit is implemented using conventional 1.2 /spl mu/m double-poly CMOS technology, and it occupies a silicon area of about 0.08 mm/sup 2/. Extensive post-layout simulations indicate that the circuit has a typical input-to-output propagation delay of less than 3 ns, and the test circuit is shown to operate reliably when consecutive 31-b input vectors are applied at a rate of up to 16 Mvectors/s. With its demonstrated data processing capability of about 500 Mb/s, the CTL-based (31,5) parallel counter offers a number of application possibilities, e.g., in high-speed parallel multiplier arrays and data encoding circuits.