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Single commercially available ic-based electronically controllable voltage-mode first-order multifunction filter with complete standard functions and low output impedance
(2021-11-01)
Jaikla, Winai
;
Buakhong, Unchittha
;
Siripongdee, Surapong
;
Khateb, Fabian
;
Sotner, Roman
This paper presents the design of a voltage-mode three-input single-output multifunction first-order filter employing commercially available LT1228 IC for easy verification of the proposed circuit by laboratory measurements. The proposed filter is very simple, consisting of a single LT1228 as an active device with two resistors and one capacitor. The output voltage node is low impedance, resulting in an easy cascade-ability with other voltage-mode configurations. The proposed filter provides four filter responses: low-pass filter (LP), high-pass filter (HP), inverting all-pass filter (AP−), and non-inverting all-pass filter (AP+) in the same circuit configuration. The selection of output filter responses can be conducted without additional inverting or double gains, which is easy to be controlled by the digital method. The control of pole frequency and phase response can be conducted electronically through the bias current (I<inf>B</inf>). The matching condition during tuning the phase response with constant voltage gain is not required. Moreover, the pass-band voltage gain of the LP and HP functions can be controlled by adjusting the value of resistors without affecting the pole frequency and phase response. Additionally, the phase responses of the AP filters can be selected as both lagging or leading phase responses. The parasitic effects on the filtering performances were also analyzed and studied. The performances of the proposed filter were simulated and experimented with a ±5 V voltage supply. For the AP+ experimental result, the leading phase response for 1 kHz to 1 MHz frequency changed from 180 to 0 degrees. For the AP− experimental result, the lagging phase response for 1 kHz to 1 MHz frequency changed from 0 to −180 degrees. The design of the quadrature oscillator based on the proposed first-order filter is also included as an application example.
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Exponentially tunable voltage controlled quadrature oscillator
(2017-10-19)
Sotner, Roman
;
Jerabek, Jan
;
Petrzela, Jiri
;
Domansky, Ondrej
;
Jaikla, Winai
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.
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Comparison of Two Solutions of Quadrature Oscillators With Linear Control of Frequency of Oscillation Employing Modern Commercially Available Devices
(2015-11-23)
Sotner, Roman
;
Jerabek, Jan
;
Langhammer, Lukas
;
Polak, Josef
;
Herencsar, Norbert
This paper proposes two circuits of frequency-controlled oscillators, whose structures are based only on simple commercially available active elements with minimum number of terminals, in particular, the differential voltage buffer, controllable voltage amplifier and electronically controllable current conveyor. Two methods for achieving linear control (tuning) of frequency of oscillations (FO) are discussed. The first method employs a simple structure. However, the generated signal level (amplitude) depends on the tuning process. This is a drawback of this method. The second method solves this drawback completely, and the generated signals have constant amplitudes during the tuning of FO. The expected behavior is confirmed by laboratory experiments utilizing commercially available high-speed active elements (current- and voltage-mode multipliers, video difference amplifier). Operational range was tested from frequencies of hundreds of kHz up to frequencies of tens of MHz.
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Novel first-order all-pass filter applications of z-copy voltage differencing current conveyor
(2015-08-01)
Sotner, Roman
;
Herencsar, Norbert
;
Jerabek, Jan
;
Vrba, Kamil
;
Dostal, Tomas
The application of z-copy voltage differencing current conveyor (ZC-VDCC) in simple and interesting first-order allpass 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.

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