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Voltage-mode biquad filter using three lt1228s with independent and electronic control of center frequency and quality factor
(2023-01-01)
Wai, May Phu Pwint
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Jaikla, Winai
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Chaichana, Amornchai
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Suwanjan, Peerawut
;
Chanapromma, Chaiyan
In this paper, we describe a voltage-mode (VM) biquad universal filter with one input and four outputs that can be tuned electronically. The filter proposed here is composed of three LT1228 commercial integrated circuits (ICs), seven resistors and two grounded capacitors. The proposed versatile biquad filter simultaneously provides four filtering functions: An inverting low-pass filter (LP), an inverting high-pass filter (HP), a non-inverting bandpass filter (BP), and an inverting notch filter (BR) without changing its topology. Employing two grounded capacitors minimizes the influence of parasitic resistances and capacitances on the proposed circuit's performance. Also, the output voltage nodes of the HP and BR functions have low output impedances. This means that these two filtering functions don't need voltage buffers to connect to other voltage-mode topologies. The center frequency (ω<inf>0</inf>) of the presented filter is electronically controlled and does not influence the quality factor (Q). In addition, they can also be tuned linearly without affecting each other. PSPICE software was used to analyze the modelling results, while a laboratory experiment was performed using LT1228 commercial ICs.
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The voltage-mode first order universal filter using single voltage differencing differential input buffered amplifier with electronic controllability
(2022-04-01)
Duangmalai, Danupat
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Suwanjan, Peerawut
In this research contribution, the electronically tunable first-order universal filter employing a single voltage differencing differential input buffered amplifier (VD-DIBA) (constructed from two commercially available integrated circuit (IC): the operational transconductance amplifier, IC number LT1228, and the differential voltage input buffer, IC number AD830), one capacitor and two resistors. The features of the designed first order universal filter are as follows. Three voltage-mode first-order functions, low-pass (LP), all-pass (AP) and high-pass (HP) responses are given. The natural frequency (ω<inf>0</inf>) of the presented configuration can be electronically adjusted by setting the DC bias current. Moreover, the voltage gain of the LP and HP filters can be controllable. The phase responses of an AP configuration can be varied from 00 to -1800 and 1800 to 00. The power supply voltages were set at ±5 V. Verification of the theoretically described performances of the introduced electronically tunable universal filter was proved by the PSpice simulation and experiment.
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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
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Buakhong, Unchittha
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Siripongdee, Surapong
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Khateb, Fabian
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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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A transconductance-mode multifunction filter with high input and high output impedance nodes using voltage differencing current conveyors (Vdccs)
(2020-12-01)
Siripruchyanun, Montree
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Jaikla, Winai
The design of transconductance-mode multifunction biquad filter containing three input voltage nodes and single-output current node is proposed. Its circuit principle is emphasized on employing Voltage Differencing Current Conveyor (VDCC) to be an active building block. The proposed filter description uses three VDCCs co-working with two grounded capacitors and three grounded resistors. The synthesis of the proposed multifunction filter is based on avoidance of using multiple-output active elements to achieve commercially available integrated circuits for practical imple-mentation. Additionally, without multiple-output active element, it can alleviate current tracking error from the current mirrors used in output ports. It also decreases the amounts of the transistors inside the active elements. The proposed multifunction filter offers all 5 filter functions, which are non-inverting Low-Pass (LP), non-inverting High-Pass (HP), non-inverting Band-Pass (BP), non-inverting Band-Reject (BR) and also non-inverting All-Pass (AP) functions from same circuit topology under different circuit condition for input signals. Furthermore, the natural frequency for all filtering responses is independently achieved from the bandwidth or the quality factor of the proposed fil-ter. For cascade-able connectivity, the output current port indeed provides a high impedance. In addition, the magnitude of the output current for all filtering functions can be resistively adjusted. The consideration for non-ideal case of the presented multifunction filter is also analyzed. The simulation and experimental results of the presented transconductance multifunction biquad filter based on VDCC practically implemented by the commercially available ICs, LM13700 and AD844 can validate the theoretical anticipation.
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0.5 V fully differential universal filter based on multiple input OTAs
(2020-01-01)
Jaikla, Winai
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Khateb, Fabian
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Kumngern, Montree
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Kulej, Tomasz
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Ranjan, Rajeev Kumar
The design of a low-power, low-voltage, fully-differential universal biquad filter is presented in this work, which is constructed from four multiple-input gate-driven operational transconductance amplifiers (MI-OTAs) along with one passive resistor and two passive capacitors. The scheme of presented biquad filter has three high-input impedance voltage nodes and single output voltage node. Five unity gain filtering functions, all-pass (AP), low-pass (LP), band-pass (BP), high-pass (HP) and band-stop (BS) responses, are obtained. The selection of output filtering responses is obtained without the need of component matching condition, inverting or double input voltage. With this feature, it can be easily controlled with digital programming. The quality factor (Q) and angular frequency (ω<inf>0</inf>) are electronically and independently tuned. Moreover, the adjustment of ω<inf>0</inf> and Q can be done without affecting the voltage gain. A workability of the design is confirmed via Cadence software and the Spectre simulator based on the 180 nm TSMC CMOS technology parameters. The proposed fully differential filter operates with 0.5 V supply voltage. The results verify that the proposed filter dissipates the total power of 53.3 nW. Additionally, the dynamic range (DR) of band-pass filtering function is 63 dB for 2% third intermodulation distortion (IMD). Also, the simulated RMS value of the band-pass filtering noise is 45 µV.
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Electronically controlled voltage mode first order multifunction filter using low-voltage low-power bulk-driven OTAs
(2019-09-01)
Jaikla, W.
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Talabthong, Pruedchawat
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Siripongdee, Surapong
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Supavarasuwat, Piya
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Suwanjan, Peerawut
In this paper, a new versatile voltage mode first order filter using low-voltage low-power bulk-driven OTAs is presented. The proposed filter with two high impedance input-voltage nodes and single output-voltage node consists of two OTAs, one grounded capacitor and one grounded resistor. Three filtering responses, low-pass (LP), high-pass (HP) and all-pass (AP) are obtained by appropriately applying the input signal into the input nodes. The natural frequency (ω<inf>0</inf>) can be electronically tuned by the bias current. In case of all-pass filter, its phase response is electronically controlled by adjusting only single bias current. With this feature, it doesn't need to simultaneously change two bias currents or two passive element values. The performances of the proposed filter were evaluated via PSPICE simulations using CMOS 0.18 μm TSMC technology parameters (level 7) with ±0.4 V supply voltages. The proposed filter consumes 47.2 μW. To obtain the actual testing results, the proposed filter was also experimented using commercially available IC, LM13700. Moreover, the three phases sinusoidal oscillator based on proposed first order high-pass filter was designed and investigated by PSPICE simulation and experiment.
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Exponentially tunable voltage controlled quadrature oscillator
(2017-10-19)
Sotner, Roman
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Jerabek, Jan
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Petrzela, Jiri
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Domansky, Ondrej
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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
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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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Novel first-order all-pass filter applications of z-copy voltage differencing current conveyor
(2015-08-01)
Sotner, Roman
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Herencsar, Norbert
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Jerabek, Jan
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Vrba, Kamil
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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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Novel oscillator based on voltage and current Gain adjusting used for control of oscillation frequency and oscillation condition
(2013-06-28)
Sotner, R.
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Jerabek, J.
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Jaikla, W.
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Herencsar, N.
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Vrba, K.
The paper deals with novel controllable oscillator where two types of electronic control are used. Proposed second-order circuit contains current follower, adjustable current amplifier, adjustable voltage amplifier, two resistors and two grounded capacitors. Oscillation frequency is tuned by voltage gain of used voltage amplifier that is represented by high-frequency voltage-mode multiplier. Oscillation condition is automatically regulated by current gain of the adjustable current amplifier which is based on current-mode multiplier. Experimental results confirmed workability of the circuit.

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