Modified optical OR and AND gates

This paper deals with optical OR and AND gate, using unijunction transistor (UJT), light emitting diode (LED), and photo-resistor (LDR). Effort is made to extend the development of the gates using UJT, LDR, and LED to work at 1.8 Vdc instead of 3 Vdc. The power dissipation is approximately 2 mW. These optical gates find application in the field of instrumentation, optical logic isolators, and fiber optics systems where intrinsic safety is of prime importance rather than speed of operation

An Operational Transconductance Amplifiers Based Sinusoidal Oscillator Using CNTFETs

A new sinusoidal oscillator using Carbon Nanotube Field Effect Transistors (CNTFET) based Operational Transconductance Amplifiers (CNOTA) with grounded capacitors is presented in this paper. The proposed current-mode oscillator thus implemented and having grounded capacitor feature, fulfils the need for realizations of systems used in combination with various other systems/ subsystems - both voltage-mode and current mode. It also ensures simplicity in implementation by using a single-ended CNOTA. The analytical model is given for the circuit leading to fulfilment of the condition of oscillation at tuned frequency. The proposed sinusoidal oscillator is primarily used in the field of signal dispensation applications, telecommunication networks, communication-equipment and control modules. The benefits derived from the introduced model are validated by simulation carried out at a supply voltage of ± 1.8V in Cadence virtuoso using spectre model libraries. They are further tested with the aid of 32 nm model of Carbon Nanotube Field Effect Transistor (CNTFET) technology obtained through open source. The proposed design (and the model provided) is found to be in good agreement with the obtained results

FinFET based 4-BIT input XOR/XNOR logic circuit

In this paper a structure for direct 4-BIT XOR/XNOR logic cell is proposed. This structure is proposed using pass transistor logic with FinFETs. This structure has less delay for the reason that its critical path consists of a minimum number of transistors. The basic advantage of this circuit is their symmetry in the logic. This design has a full voltage swing at the outputs and hence it has the good driving capability. The proposed design produces perfect outputs, even at low voltages and at high frequencies with the lesser transistor count. The proposed design is simulated using Cadence 20 nm FinFET technology at various supply voltages assorting from +0.6 V to +0.9 V. The simulation results illustrate that the proposed design has less delay and as well as less power consumption

CCII+ based novel waveform generator with grounded resistor/capacitor for tuning

This paper presents a new topology for waveform-generation using two current conveyors, and a grounded capacitor or a resistor for tuning. It uses current-conveyors in place of voltage op-amps to offer better linearity, bandwidth, slew rate and thermal stability. Measured results obtained using commercially available devices AD844AN and passive components show excellent linearity and tunability for both grounded resistor and capacitor topologies over the range of interest. Component sensitivity and temperature-sensitivity from -150°C to +150°C are studied. A comparison with existing candidate-designs shows superiority of the proposed design on all aspects. Grounded-connection of tuning components makes digital control easy

Analysis of Two New Voltage Level Converters With Various Load Conditions

The use of level converter in dual supply voltage circuits is one of the most effective ways to reduce power consumption. To prevent static current, level converter is introduced as an interface at each low-to-high boundary. The design of an efficient level converter with least power consumption and overheads delay is one of the major design constraints. In this paper, two new level converter circuits with low power consumption are proposed for less propagation delay and load adaptability. The proposed level converter circuits are examined using cadence and the design parameters of a 180 nm CMOS process. The simulation results exhibit that proposed level converter can reduce propagation delay and increase speed over the existing circuits available. These level converters are simulated for different loads and operating conditions. The proposed level converter can operate at different values of VDDL as +1 V, +1.8 V, +2 V and VDDH of +3.3 V. The topology reports low sensitivity and has features suitable for VLSI implementation. The proposed circuits are suited for low power design without degrading performance.  </p

Four new oscillators using operational transresistance amplifier

In this paper, four new sinusoidal waveform generators based on the operational transresistance amplifier (OTRA) are presented. The first proposed circuit is a minimum component RC sinusoidal oscillator circuit with one OTRA and a few passive components. The second and third proposed circuits consist of one OTRA and a few passive components, among them two passive components are connected to ground. These circuits are able to control the condition of oscillation and frequency of oscillation independently. The fourth proposed quadrature oscillator circuit uses two OTRAs as main active building blocks and a few external passive components to generate the oscillations. The commercially available IC AD844AN has been adopted to implement the proposed circuits on a laboratory breadboard with external passive components. Both the SPICE simulation and experimental results are given to verify the theoretical analysis of the proposed circuits

Optical Co-Incidence Gate

The paper explains Optical co-incidence gate, realized using Unijunction transistors (UJT), Light emitting diodes (LED) and Photo-resistors (LDR), which works on 1.8Vdc instead of 3Vdc. The power dissipation of the designed gate is only 3 mW. This optical gate finds application in the field of Mechatronics, Instrumentation and Fiber optics systems where intrinsic safety is of prime importance rather than speed of operation. Key words: Bistability, Intrinsic safety, and Low speed. (Af. J. of Science and Technology: 2002 3(2): 114-117

Three Microwave Frequency Dividers Using Current Source/Sink and Modified Current Source Inverters

In a preceding paper Carlos E. Saavedra, 2005, established that frequency division can be achieved with the use of inverter rings and transmission gates. In this paper, we suggest three modified circuits which obtain the similar function, namely, using Current Sink Inverter, Current Source Inverter, and Modified Current Source Inverter. The performances of the proposed circuits are examined using Cadence and the model parameters of a 45 nm CMOS process. The simulation results of the three circuits are presented and are compared. We also present the results of a simple but effective novel technique to reduce clock skew between real and complementary clock signals and the corresponding improvement achieved in maximum frequency of operation. One of the proposed circuits can operate at up to 8.2 GHz input while performing a divide-by-4 operation

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