High input impedance voltage-mode universal filter and its modification as quadrature oscillator using VDDDAs

The second order universal voltage-mode filter using voltage differencing differential difference amplifiers (VDDDAs) has been proposed. It has high input impedance voltage-mode biquad filter with orthogonal tune of natural frequency and quality factor. The proposed filter simultaneously provides five filter responses: low-pass (LP), high-pass (HP), band-reject (BR), all-pass (AP) and band-pass (BP) in the same circuit topology. The natural frequency and quality factor can be tuned electronically and orthogonally dc bias current. The output impedance at output nodes HP, AP and BR has low impedance which can connect to other circuit without the use of voltage buffers. The proposed filter consists of three VDDDAs, one grounded resistor and two grounded capacitors. This makes the proposed filter suitable for integrated circuit development. With slightly modifying the proposed filter, the voltage-mode qudrature sinusoidal oscillator with low output impedance and independent control of condition of oscillation (CO) and frequency of oscillation (FO) has been achieved. The results shown in this paper are from PSPICE simulation and experiment to validate the proposed circuits

Novel first-order all-pass filter applications of z-copy voltage differencing current conveyor

The application of z-copy voltage differencing current conveyor (ZC-VDCC) in simple and interesting first-order all-pass sections has been studied in the present paper. The solutions presented here have presumptions for direct electronic control. Some of proposed circuits offer curious possibilities of control. Electronic controllability of the VDCC allows simultaneous zero and pole frequency adjusting, separated zero or pole frequency adjusting or migration of zero from left half plane to right half plane of complex space. Behavioral models of VDCC based on commercially available devices are proposed and selected type of all-pass section was verified by simulations and also by measurements. Results of simulations, experiments, and theoretical proposal are compared. Experiments confirm workability of proposed behavioral equivalent circuit in bandwidths to units of MHz

Design of Novel Precise Quadrature Oscillators Employing ECCIIs with Electronic Control

In this paper, an interesting design of precise quadrature oscillator employing electronically controllable current conveyors of the second generation (ECCII) is presented. The main purpose of this paper is to show advantages and features of direct electronic control of application by an adjustable current gain where help of signal flow graph approach was used to clearer and visual understanding of the design. The discussed circuit and its presented modification have several favorable features such as grounded capacitors, independent electronic adjusting of oscillation frequency and condition of oscillation by the current gain and easy automatic gain control circuit (AGC) implementation (non-ideal effects of tuning process on output amplitudes are suppressed). Oscillator was designed for frequency band of units of MHz and tested with two types of inertial AGCs. Theoretical presumptions were confirmed by laboratory experiments.Czech Science FoundationGrant Agency of the Czech Republic [102/11/P489, 102/09/1681]; operational program Education for competitiveness; SIX project [CZ.1.05/2.1.00/03.0072]; operational program Research and Development for Innovation; EU ECOP [EE.2.3.20.0094, CZ.1.07/2.2.00/28.0062]; [CZ.1.07/2.3.00/20.0007 WICOMT]; [CZ.1.07/2.3.00/30.0039]Research described in the paper was supported by Czech Science Foundation projects under No. 102/11/P489 and No. 102/09/1681. The support of the project CZ.1.07/2.3.00/20.0007 WICOMT, financed from the operational program Education for competitiveness, is gratefully acknowledged. The described research was performed in laboratories supported by the SIX project; the registration number CZ.1.05/2.1.00/03.0072, the operational program Research and Development for Innovation and supported by the project CZ.1.07/2.3.00/30.0039. This research work is also funded by projects EU ECOP EE.2.3.20.0094, CZ.1.07/2.2.00/28.0062

Simple Oscillator with Enlarged Tunability Range Based on ECCII and VGA Utilizing Commercially Available Analog Multiplier

This work presents an example of implementation of electronically controllable features to an originally unsuitable circuit structure of oscillator. Basic structure does not allow any electronic control and has mutually dependent condition of oscillation (CO) and frequency of oscillation (FO) if only values of passive elements are considered as the only way of control. Utilization of electronically controllable current conveyor of second generation (ECCII) brings control of CO independent of FO. Additional application of voltage amplifier with variable gain in both polarities (voltage-mode multiplier) to feedback loop allows also important enlargement of the range of the independent FO control. Moreover, our proposal was tested and confirmed experimentally with commercially available active elements (“Diamond transistor”, current-mode multiplier, voltage-mode multiplier) in working range of tens of MHz

Floating capacitance multiplier simulator for grounded RC colpitts oscillator design

Actively simulated grounded floating capacitance multipliers have been used in several applications ranging from filter to oscillator design as well as cancellation of parasitic capacitances. In this paper, a new electronically-controllable floating lossless capacitance multiplier (C-Multiplier) circuit is presented, which employs only one Voltage Differencing Current Conveyor (VDCC), one grounded capacitor and one grounded resistor. Since the new simulated C-Multiplier uses a grounded capacitor; accordingly, it is suitable for IC fabrication. A number of simulations with employing commercially available devices through PSPICE program are accomplished to demonstrate the workability, performance, and effectiveness. Functionality of the proposed circuit is verified through its application in a linearly tunable quadrature oscillator, which one is derived from Colpitts oscillator