A translinear-based true RMS-to-DC converter using only npn BJTs

A true rms-to-dc converter based on the explicit computation technique is proposed in this paper. Since the scheme utilizes translinear principle circuits to realize current-mode squarer, averaging and square root circuits, only npn bipolar junction transistors are required. The conversion circuit has wide-band frequency response and can be operated with single supply voltage at 2 V. PSPICE simulation and experimental results show good agreement with the theoretical predictions.     

Full-wave rectifiers based on operational transconductance amplifiers

The implementation of full-wave rectifiers using operational transconductance amplifiers (OTAs) as only main active circuit elements is presented in this paper. The proposed scheme makes use of the characteristic of the differential amplifier inside the OTA and avoids the use of diodes. The typical problems of the OTA circuit, the input voltage swing limitation and the temperature dependence of the OTA transconductance gain, have been improved. Simulation and experimental results demonstrate the performance of the proposed rectifier are included.     

Impact of cosolvents (polyols) on globular protein functionality: Ultrasonic velocity, density, surface tension and solubility study

The objective of this study was to understand how cosolvents influence the molecular and functional properties of globular proteins in aqueous solutions. The ultrasonic velocity, density and adiabatic compressibility of cosolvent solutions (0–50 wt% sorbitol or glycerol) were measured in the absence and presence of a globular protein (1 wt% β-lactoglobulin) at 30 °C. These measurements were used to calculate the partial specific apparent volume and adiabatic compressibility of the protein. The protein's volume decreased and its compressibility increased in the presence of high cosolvent concentrations, which were attributed to changes in the properties of the protein interior and solvation layer. Sorbitol was more effective than glycerol at decreasing the protein volume at high cosolvent concentrations, which may be because glycerol has some surface activity and may therefore accumulate around hydrophobic regions on the protein surface. Our data were used to account for the observation that sorbitol is more effective than glycerol at increasing the thermal stability and self-association of the β-lactoglobulin. A better understanding of the influence of protein–cosolvent–solvent interactions on the functionality of globular proteins may facilitate the design of protein-based products.     

Modulation of thermal stability and heat-induced gelation of β-lactoglobulin by high glycerol and sorbitol levels

The influence of glycerol and sorbitol on the thermal stability and heat-induced gelation of β-lactoglobulin (β-lg) in aqueous solutions was investigated. The thermal stability of β-lg was characterized by measuring the thermal denaturation temperature (T_m) using differential scanning calorimetry, while its gelation properties were characterized by measuring the gelation temperature (T_gel) and final gel rigidity (G^∗) using dynamic shear rheology. All experiments were carried out using aqueous solutions containing 10% (w/w) β-lg, glycerol (0–70% w/w) or sorbitol (0–55% w/w), and 5 mM phosphate buffer (pH 7.0). No salt was added to these solutions so that there was a relatively strong electrostatic repulsion between the protein molecules, which usually prevents gelation. When the cosolvent concentration was increased from 0% to 50%, T_m increased from 74 to 86 °C for sorbitol, but only from 74 to 76 °C for glycerol, which indicated that sorbitol was much more effective at stabilizing the native state of the globular protein than glycerol. Protein solutions containing sorbitol (0–55%) did not form a gel after heating, but those containing glycerol formed gels when the cosolvent concentration exceeded about 10%, with G^∗ increasing with increasing glycerol concentration. We attribute these effects to differences in the preferential interactions of polyols and water with the surfaces of native and heat-denatured proteins, and their influence on the protein–protein collision frequency.     

Electronically Tunable Current-Mode Universal Filter Employing Only Plus-Type Current-Controlled Conveyors and Grounded Capacitors

A new current-mode current-controlled three-input single-output universal filter, which employs only five plus-type second-generation current-controlled current conveyors (CCCIIs) and two grounded capacitors, is presented in this paper. The proposed configuration provides lowpass, bandpass, highpass, bandstop, and allpass current responses at a high impedance terminal, which enables easy cascadability of the circuit. The filter also offers independent electronic control of the natural frequency ω_o and the quality factor Q through adjusting of the bias current of the CCCII. Derived analytical expressions for the filter parameter deviations due to CCCII nonidealities are also included. PSPICE simulation results are performed to confirm the theoretical analysis.     

PARAMETERS INFLUENCING TONER CHARGING CHARACTERISTICS IN ELECTROPHOTOGRAPHIC PRINTING

ABSTRACT

The charge-to-mass ratio, q/m, of a two-component developer is the important factor in an electrophotographic system, since the toner charge controls the developed tone mass and the print quality. This article investigates the charging properties of differently shaped toners (spherical and irregular), and carrier particles that differ in their composition and surface oxide layer thickness by adjusting the applied current. The parameters for toner charging involving the mixing force, the toner concentration, the shape of the toner, the carrier type, and the current of the carrier surface are studied. The print quality is evaluated by focusing on the solid density, 60 and 40% halftone densities, background density, and edge sharpness of the characters. An explanation of the force between the toner and carrier particles is proposed.     

An integrable temperature-insensitive gm –RC quadrature oscillator

A novel g_m –RC quadrature oscillator using operational transconductance amplifiers (OTAs) and grounded passive elements is proposed. The circuit provides two quadrature outputs of equal magnitude and the oscillation frequency is insensitive to temperature. The oscillation frequency can be linearly and electronically controlled without affecting the condition of oscillation. The active ω₀-sensitivity has been shown to be small. Experimental and simulation results that demonstrate the performance of the proposed oscillator are also included.     

Sinusoidal frequency doubler and full-wave rectifier based on translinear current-controlled current conveyors

A circuit design technique that employs translinear current-controlled current conveyors as active circuit elements to design a sinusoidal frequency doubling and full-wave rectifying circuit is proposed. The circuit can realize the sinusoidal frequency doubler and full-wave rectifier without changing the circuit configuration. The proposed frequency doubling and rectifying action is exploited from the translinear characteristic of the current conveyor. Simulation and experimental results are given to confirm the theoretical predictions.     

On the realization of electronically current-tunable CMOS OTA

A CMOS operational transconductance amplifier (OTA) called as an EOTA, where its transconductance gain can be electronically and linearly tuned is proposed in this paper. The realization method is achieved by squaring the transconductance gain of the balanced CMOS OTA. The EOTA transconductance gain can be linearly tuned by an external bias current for three decades. The linear input-voltage range of about 1 Vp with less than 1% nonlinearity is obtained. The usefulness of the proposed EOTA is demonstrated through application example with a current multiplier. The performance of the proposed circuit is discussed and confirmed through PSPICE-simulation results.     

High output impedance current-mode universal filter employing dual-output current-controlled conveyors and grounded capacitors

A novel current-controlled two-input three-output current-mode universal filter, which employs only three dual-output controlled-controlled current conveyors (DOCCCIIs) and two grounded capacitors, is presented in this paper. The proposed configuration provides inverting-type lowpass, noninverting-type lowpass, inverting-type bandpass, noninverting-type bandpass, highpass, bandstop and allpass current responses at a high impedance terminal, which enable easy cascadability. The filter also offers an independent electronic control of the natural frequency ω_o and the parameter ω_o/Q through adjusting the bias current of the DOCCCII. No critical matching condition is required for realizing all the filter responses, and all the incremental parameter sensitivities are low. The performances of the proposed circuit are simulated with PSPICE to confirm the presented theory.