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Differentiator circuits with scalable and electronically adjustable time constant and their application in phase shift evaluation
(2025-09-01)
Sotner, Roman
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Polak, Ladislav
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Petrzela, Jiri
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Semenov, Dmitrii
;
Langhammer, Lukas
Two novel scalable and electronically adjustable differentiator designs are presented in this paper. These designs are based on special variable gain amplifiers extending well-known concept of standard single operational amplifier-based differentiators. The key novelty lies in their scalability, which allows for an enhanced time constant value by adjusting the ratio of resistors. Simultaneously, the special form of gain control using a DC voltage offers wide electronic tunability. The solution performs high input and low output impedance, both independent of frequency. Experimental testing demonstrated time constant adjustments in two configurations: from 64 ns to 4.5 µs (a ratio of maximal and minimal value 70) and from 8.7 µs to 183 µs (a ratio of 21). As an application example, the proposed differentiator is utilized in the design of a readout system for an absolute phase shift difference to pulse width ratio converter, suitable for monitoring a very slow phenomenon such biosignals.
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1 V Electronically Tunable Differential Difference Current Conveyors Using Multiple-Input Operational Transconductance Amplifiers
(2024-03-01)
Kumngern, Montree
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Khateb, Fabian
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Kulej, Tomasz
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Langhammer, Lukas
This paper presents electronically tunable current conveyors using low-voltage, low-power, multiple-input operational transconductance amplifiers (MI-OTAs). The MI-OTA is realized using the multiple-input bulk-driven Metal Oxide Semiconductor transistor (MIBD-MOST) technique to achieve minimum power consumption. The MI-OTA also features high linearity, a wide input range, and a simple Complementary Metal Oxide Semiconductor (CMOS). Thus, high-performance electronically tunable current conveyors are obtained. With the MI-OTA-based current conveyor, both an electronically tunable differential difference current conveyor (EDDCC) and a second-generation electronically tunable current conveyor (ECCII) are available. Unlike the conventional differential difference current conveyor (DDCC) and second-generation current conveyor (CCII), the current gains of the EDDCC and ECCII can be controlled by adjusting the transconductance ratio of the current conveyors. The proposed EDDCC has been used to realize a voltage-to-current converter and current-mode universal filter to show the advantages of the current gain of the EDDCC. The proposed current conveyors and their applications are designed and simulated in the Cadence environment using 0.18 μm TSMC (Taiwan Semiconductor Manufacturing Company) CMOS technology. The proposed circuit uses ±0.5 V of power supply and consumes 90 μW of power. The simulation results are presented and confirm the functionality of the proposed circuit and the filter application. Furthermore, the experimental measurement of the EDDCC implemented in the form of a breadboard connection using a commercially available LM13700 device is presented.
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Integer- And fractional-order VCO using non-inertial amplitude stabilization and modern active elements
(2020-04-28)
Sotner, Roman
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Petrzela, Jiri
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Jerabek, Jan
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Langhammer, Lukas
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Polak, Josef
This paper introduces design of the linearly tunable quadrature voltage-controlled oscillator (VCO) using modern off-the-shelf active elements suitable for the design of electronically adjustable applications. The simplified topology was achieved using non-inertial stabilization of amplitude. It allows targeting adjustability of the oscillation frequency only into lossless integrator part of the topology. This arrangement simplifies the design and the tenability also. Derived symbolical expressions indicate that gain adjustment of used amplifiers (that are still in single path) does not influence amplitude and phase shift ratio of generated waveforms, which is a beneficial feature. The performances of the circuit are tested experimentally in band of units of MHz and results confirmed expected behavior. Initial study of the oscillator with fractional-order capacitors is presented and discussed. Results are supported by laboratory measurements.
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Voltage Differencing Current Conveyor Differential Input Transconductance Amplifier: Novel Active Element and Its Resistorless Filtering Application
(2019-10-01)
Sotner, Roman
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Jerabek, Jan
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Langhammer, Lukas
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Petrzela, Jiri
;
Jaikla, Winai
This paper introduces novel modification of active element based on current conveyor transconductance amplifier core abbreviated as current controlled voltage differencing current conveyor differential input transconductance amplifier (CC-VDCCDITA). The active element is implemented by recently developed and manufactured IC modular device based on I3T25 0.35 μm ON Semiconductor CMOS process. Active element uses three internal active cells of this IC device for construction of the CC-VDCCDITA. An application example of proposed element in simple special resistor-less electronically adjustable biquadratic filter is shown. Brief comparison with state-of-the-art solutions indicates beneficial features of proposed solution. Simulation results in Cadence IC tool accompany precise laboratory experimental measurements with real prototype.
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Operational frequency bandwidth rescalable implementations of constant phase devices
(2019-04-01)
Sotner, Roman
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Jerabek, Jan
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Langhammer, Lukas
;
Polak, Ladislav
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Jaikla, Winai
This paper presents and verifies a method for rescalability of operational bandwidth in constant phase devices (two-port elements, two-port transfer blocks). Most importantly, in comparison with a standard approach, it allows to utilize suitable values of capacitance in the case of operation at low-frequency bands. The capacitance multipliers based on a controllable variable gain amplifier are implemented in examples of simple fractional-order systems (two-port integrators). These examples consist of novel bilinear immittances with independently settable zero and pole frequency coordinates, based on widespread commercially available current conveyors of second generation. The capacitance multiplier extends features of the bilinear immittance and full implementation of the system. PSpice simulations, using off-the-shelf elements, confirm operability of the proposed concept.
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Reconnection-less Reconfigurable Filter and its Application into Adaptive Circuit
(2018-08-20)
Sotner, Roman
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Jerabek, Jan
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Petrzela, Jiri
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Langhammer, Lukas
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Domansky, Ondrej
This paper presents special topology of a reconnection-less reconfigurable second-order filter. Its features of available transfer functions are unique, because none of the previously reported solutions provides similar features. Our concept is easily implementable thanks to the simple commercial active devices as shown in the paper. The design specifications and transfer responses are analyzed by PSpice simulations. Application example of the high-pass response with adjustable low-frequency stop-band attenuation in adaptive signal processing is shown. All results are following theoretical expectations.
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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
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Jerabek, Jan
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Langhammer, Lukas
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Polak, Josef
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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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