Ondrej Domansky

Special electronically reconfigurable lossy/lossless integrator in application of functional generator

This paper deals with idea of an electronically reconfigurable integrator utilized in nonlinear application of functional generator and study of its features in this circuit. The integrator can be electronically readjusted to lossy and lossless type as well as this integrator also offers electronic tuning of time constant. Possibility of simple electronic reconfiguration provides generation of square wave and selection to generate triangular or exponential (relaxation) output waveforms in node of working capacitor. Intentions of synthesis and design were confirmed by PSpice simulations.

Higher order differentiator block for synthesis of controllable frequency dependent elements

This paper presents structure of generally nth-order differentiator transfer block serving for purpose of integer order or fractional order immittance (impedance) synthesis. Presented structure of the differentiator is based on electronically controllable current conveyors (ECCIIs), current conveyor of second generation (CCII) and electronically controllable gain amplifier (VGA). This structure was applied as example of 3rd order differentiator and frequency dependent negative resistors (FDNRs) of integer (as well as fractional) order. Proposed applications offer electronic controllability of time constant, magnitude value and reconfigurability of impedance character (between positive and negative). PSpice simulations were performed in order to verify presented concepts.

Exponentially tunable voltage controlled quadrature oscillator

This paper deals with appropriate method of tunability extension in quadrature oscillators. Exponential dependence of frequency of oscillations on DC control voltage is created in lossless integrators by utilization of two exponentially controlled variable gain amplifiers and diamond transistors. Proposed solution maintains all beneficial features (especially independent levels of output waveforms on tuning process) of the oscillator concept employing two lossless integrators in the single loop and electronically controllable negative resistor serving for adjusting of condition of oscillations. PSpice verifications based on simulations of macromodels of used active devices confirmed doubled tunability range in comparison to standard linear control of frequency obtained for the same change of DC driving voltage.

A 1+α Low-Pass Fractional-Order Frequency Filter with Adjustable Parameters

A novel solution of a fractional order low-pass type frequency filter is presented. The proposed structure comprises of two Double-Output Current Followers (DO-CFs), two Multi-Output Current Followers (MO-CFs) and two Adjustable Current Amplifiers (ACAs). The slope of the transition between the band-pass and band-stop region can be adjusted by intentional control of the order in range from 1 to 2 given by the change of values of resistors and current gains of ACA elements. The proposal is supported by PSpice simulation using transistor-level simulation models of employed active elements.

Single active parameter tunable simple band-pass filter: Methods for tunability range extension

This paper compares three possible methods of adjusting center frequency in a second order band-pass filter using a single active parameter. Limited range of driving voltages serving for tuning of electronically controllable applications is the problem of modem low-voltage systems due to reduced power supply voltage. Therefore, methods how to obtain similar bandwidths of adjustability in comparison to standard linear control applied in systems with DC driving voltage/current range below one decade should be studied. Lossless integrator (its transconductance subpart) implemented in the structure of the filter was solved as three different subcircuits allowing three different methods of its adjusting, i.e. linear, quadratic and exponential dependence of transconductance gm on DC driving voltage Vset. This results to square root, linear and exponential dependence of center frequency of the filter on Vset. The last method allows to reach at least a four-times wider range of tunability of center frequency in comparison to standard implementation of a linearly controllable integrator in the same range of Vset. PSpice simulations confirm intended features of the proposed methods.

Current feedback operational amplifier based two-port frequency equalizer

This paper brings novel first-order bilinear two-port section (also called as two-port block). New topology reduces complexity and minimizes impact of fabrication dispersion (tolerances) of passive elements on transfer features in comparison to previously reported solutions. Developed bilinear section was applied for arbitrarily equalized transfer response operating from tenths of Hz to hundreds of kHz. Important application of bilinear section in synthesis of fractional-order differentiator and integrator was verified for mathematical order α = 0.25 operating from tens of Hz to tens of kHz, i.e. more than two decades with phase error in range of ± 3 degree. Features of proposed devices were verified by PSpice simulations.