Ali Ümit Keskin

Grounded capacitor current mode single resistance-controlled oscillator using single modified current differencing transconductance amplifier

This study proposes a current mode canonical single resistance-controlled oscillator (SRCO) circuit based on a single modified current differencing transconductance amplifier. The circuit employs grounded capacitors and provides a current output with high output impedance. The proposed circuit also enables orthogonal control of frequency and oscillation condition. The performance of the proposed SRCO is verified by means of simulation program with integrated circuit emphasis (SPICE) simulations, on-chip experiments and measurements.

Quadrature Oscillator Using Current Differencing Buffered Amplifiers (CDBA)

This paper proposes a current differencing buffered amplifier (CDBA)-based quadrature oscillator (QO) circuit which has only grounded and virtually grounded capacitors, and good sensitivity properties. Oscillation frequency of this configuration can be made adjustable by using voltage controlled elements (MOSFETs). Its performance is analysed and results of circuit simulations that verify theoretical predictions are presented. Index Terms – Quadrature oscillator, CDBA, all-pass filter

Cascadable Voltage-Mode Multifunction Biquad Employing Single OTRA

Abstract – A voltage-mode (VM), multi-input single-output (MISO) type multifunction biquad is proposed. It uses only one operational transresistance amplifier (OTRA) as the active element, while previously reported VM multifunction filters require more OTRAs. Proposed MISO type biquad configuration can realize all five different filter transfer functions. Theoretical results are verified with PSPICE simulations using a CMOS realization of OTRA.

Design of a PID Controller Circuit Employing CDBAs

Proportional-integral-derivative (PID) controllers are one of the most important control elements used in the process control industry. In practice, voltage mode circuits (e.g., operational amplifiers) are largely used in analogue controllers. However, recent developments in the areas of nanotechnologies and micro-electromechanical systems (MEMS) necessitate fast operating active analogue circuits. This paper presents a PID controller circuit based on a newly introduced active universal component, so-called current differencing buffered amplifier (CDBA), and shows that the circuit performs quite well as a PID controller and offers the benefits of a current mode structure. An example is given to illustrate the application of this new active element. The development of the overall circuit relies on concepts introduced in the frequency domain, therefore it can be used as material for undergraduate-graduate circuits, systems and control courses.

SINGLE CFA-BASED NICs WITH IMPEDANCE SCALING PROPERTIES

Negative impedance converter circuits (NICs) are important building blocks in design and manufacturing of analog and mixed mode integrated circuits. In this paper, a catalogue of single-current feedback amplifier-based negative impedance converter circuits having impedance scaling properties is proposed. Various examples are presented to illustrate the versatility of the proposed NIC circuits.

Voltage-Mode Notch Filters Using Single CDBA

Conventional Op-amps and universal resistor programmable switched-C filters are configurable as notch filters (NFs), but most of these active elements cannot operate at bandwidths higher than 100kHz. Current mode (CM) active elements provide wide bandwidths and high slew rates. On the other hand, many of today’s continuous time analog signal processing applications require voltage mode (VM) operation. Therefore, it is advantageous to implement CM active elements in VM circuits. Many VM-NF structures using CM active elements have been developed in literature. However, most of these filters require more than two active components in their realizations [1-4], and few authors report VM notch filters using single CM active elements [5-7]. A new CM active element, the current differencing buffered amplifier (CDBA) has received considerable interest in recent years [7-16]. It has been proven that the CDBA is a versatile active building block for voltage and current mode signal processing applications. Considering the CDBA-based VM-NF applications, only the work in [7] includes a single CDBA-based VM-NF, however it is not universal and has only real poles. This paper presents a set of single CDBA-based voltage mode biquadratic notch filters and reports their theoretical and experimental performance results.

Steady-state solution of loaded thermistor problems using an electrical equivalent circuit model

It may be quite difficult to find analytical solutions for some simple circuits containing a thermistor element. Iterative numerical procedures may also yield impractical or complicated operations including convergence problems. Often, it is not necessary to obtain a complete solution for the dynamic thermistor equation, but rather search for a steady-state response for a thermistor element. Here, circuit simulation algorithms such as SPICE can be helpful. In this study, an electrical equivalent circuit model for the steady-state NTC thermistor current–voltage characteristics at different ambient temperatures is proposed. The model includes a number of electrical equivalent circuit components (namely, diode, resistor and current source) for a piecewise-linear approximation to the current–voltage characteristic curve of an NTC thermistor. Once the electrical parameters of the loaded (self-heated) thermistor are computed at a given ambient temperature using this proposed model, then one may easily find its working (body) temperature. The performance of the method is demonstrated using a practical example. Advantages as well as limitations of the model are also discussed.

Detection of alveolar epithelial injury by Tc-99m DTPA radioaerosol inhalation lung scan in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is a systemic autoimmune disorder primarily involving the joints. Lung alterations in RA may be primary or secondary to pharmacological treatments and may involve the alveoli, interstitium, airways and/or pleura. Technetium-99m diethylenetriaminepentaacetic acid (Tc-99m DTPA) aerosol inhalation scintigraphy is a sensitive and noninvasive test commonly employed to assess pulmonary epithelial membrane permeability. The purpose of the this study was a) to investigate the changes of pulmonary alveolar epithelial permeability in patients with RA, b) to determine the relationship between the clearance rate of Tc-99m DTPA and pulmonary function test (PFT) results, and c) to determine the relationship between the clearance rete of Tc-99m DTPA and clinical parameters of disease. Twenty-five patients with RA but without lung alterations were included in the study. The patients were 22 females, and 3 males; mean age 53.6 ± 8.7 years. Technetium-99m DTPA aerosol inhalation scintigraphy was performed on the study and healthy control groups. Clearance half times (T1/2) were calculated by placing a mono-exponential fit on the curves. Penetration index (PI) was calculated on the first-minute image. There were no significant differences in the mean T1/2 or mean PI values between the RA patients and control subjects. No correlation was found between the mean T1/2 values of Tc-99m DTPA clearance and activity of RA, clinical values, or the spirometric measurements except FEV1/FVC and functional status in RA patients (p = 0.02, p = 0.01, respectively). However, a weak correlation was found between duration of disease and T1/2 values of Tc-99m DTPA clearance (p = 0.006). PI values tended to correlate with FEF25-75, although, this was not statistically significant (p = 0.057). This study shows that no changes occur in alveolar-capillary permeability in RA patients without lung alterations.

Electrical Circuits in Biomedical Engineering

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Comments on the "Sensor calibration and compensation using artificial neural network", by Khan S.A., Shahani D.T., Agarwala A.K.

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