Generalized gyrator implementation techniques using unity-gain cells

All possible gyrator circuits using the minimum number of voltage and current unity-gain cells are extracted, as a result of generalizing the unity gains, such that a unity gain can be + 1 or ?1. Since second-generation current conveyors (CCIIs), possessing both voltage and current unity-gain cells, are very suitable for such gyrators, it is shown that inclusion of the recently proposed ‘inverting secondgeneration current conveyor’ (ICCII) in the design enables implementation of all types of extracted gyrators. The number of possible gyrator configurations is eight, one of them being the well-known Sedra–Smith gyrator and another its x -input counterpart; both utilize only CCIIs. The remaining possible six gyrators are new and utilize ICCIIs as well. Like the Sedra–Smith gyrator, all the circuits employ a minimum number of passive elements and similar types of active components, namely CCIIs and/or ICCIIs. The effects of current conveyor non-idealities and parasitics on important gyrator applications are also investigated. A highperformance dual-output CMOS ICCII is designed and used in SPICE simulations of two important gyrator applications in order to verify the theoretical results. Also, as a design example, an elliptic filter is realized and simulated.     

Stock optimization for service differentiated demands with fill rate and waiting time requirements

We develop a computationally efficient optimization procedure to optimize stock and rationing levels for a model consisting of a single product with two priority–demand classes, given by mutually independent, stationary, Poisson demand processes. Each priority class has its own service levels requirements, defined by the class-specific fill rate and expected waiting-time levels. Order lead times are independent and identically distributed random variables. This is the first study in this setting to consider both waiting-time constraints along with fill rate requirements.     

Electronic properties of (2 x 1) and c(4 x 2) domains on Ge(001) studied by scanning tunneling spectroscopy

The surface electronic structure of Ge(001) was studied by scanning tunneling spectroscopy. The measured surface densities of states unequivocally reveal the presence of a metallic state on the (2 x 1) domains, which is absent on the c(4 x 2) domains. This metallic state, so far observed only in integral measurements, is attributed to the flip-flopping dimers that constitute the (2 x 1) domains. Our data also reveal a set of previously unresolved surface states, in perfect agreement with published theoretical predictions.     

Hydrothermal in situ preparation of phthalocyanine–TiO2 nanocomposites for photocatalytic activity under visible light irradiation

Research on Chemical Intermediates - In this study, phthalocyanine (Pc)–TiO2 nanocomposites were prepared via in situ hydrothermal method. The metal-free, zinc(II), cobalt(II), nickel(II) and...     

A new approach for high-input impedance in voltage mode filters using first-generation current conveyor in place of second-generation current conveyor

An advantage of the second-generation current conveyor (CCII) over the first-generation current conveyor (CCI) is its high-input impedance Y terminal. Thus, CCII offers cascadable voltage mode filter realisations with little efforts. However, in case of CCI this feature is difficult to achieve. This article presents a case where the CCI is able to provide cascadability for some voltage mode filter topologies, where the CCII is not. The presented approach is applied to some filter circuits from the literature and new circuits are derived with cascadability feature. Simulations are performed to verify the theoretical results.     

Component reduced all-pass filter with a grounded capacitor and high-impedance input

In the literature, opportunities of the current conveyors with reduced current gains are not adequately emphasised for filter designs. In this study, we show a new all-pass filter (APF) possibility using a current conveyor with half current gain. Although many first-order voltage mode APFs were proposed, most of them either cannot provide high input impedance and grounded capacitor features together or they provide these features with components more than necessary. The presented circuit provides both of these features using reduced number of elements. Spice simulation and experimental results are given to verify the theoretical results.     

All-pass filter for rich cascadability options easy IC implementation and tunability

This paper presents two current-mode all-pass sections, employing only grounded components, which is important from the integrated circuit (IC) implementation point of view. The use of the grounded capacitor allows the IC implementation with standard CMOS technologies. The circuits can be made electronically tunable due to grounded resistors that can be realized by using voltage controlled MOS based resistors. In addition, the circuits have both low input impedance and high output impedance for easy cascadability. The stability analysis proves that the circuits are stable. SPICE simulations and experimental results are in close agreement with the theory.     

New resistorless tunable voltage-mode universal filter using single VDIBA

To increase the universality of the recently introduced voltage differencing inverting buffered amplifier (VDIBA), this letter presents a new voltage-mode (VM) multi-input–single-output (MISO) universal filter. The proposed filter contains only single VDIBA, two capacitors, and one nMOS transistor, operated in triode region, and is used for resonance angular frequency tuning. Since in the structure no resistors are needed the filter can be classified as resistorless. The VM MISO filter compared with other active building block-based counterparts is very simple, it contains only few transistors, and has the smallest size area. Moreover, no component matching is required and it shows low sensitivity performance. The theoretical results are verified by SPICE simulations using TSMC 0.18 μm level-7 SCN018 CMOS process parameters with ±0.9 V supply voltages. In addition, the behavior of the proposed VM filter was also experimentally verified using commercially available integrated circuits OPA660 and AD830.     

High output impedance current-mode multifunction filter withminimum number of active and reduced number of passive elements

A new current-mode multifunction filter with a single input and three outputs employing only three positive type CCIIs and five passive elements is presented. The proposed filter realises three filter functions simultaneously all at high impedance outputs. No component matching is required and all passive sensitivities are low