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Single-resistance-controlled quadrature oscillator and universal biquad filter using CFOAs
(2009-12-01)
Tangsrirat, Worapong
;
Surakampontorn, Wanlop
This paper presents new single-resistance-controlled (SRC) sinusoidal quadrature oscillator and universal biquad filter circuits with reduced number of passive elements using only two current-feedback operational amplifiers (CFOAs). The first proposed oscillator configuration comprising two CFOAs, three resistors and two capacitors provides two sinusoidal voltage outputs in phase quadrature. The circuit has the advantage of independent control of the condition of oscillation and the oscillation frequency through a single resistor. The second proposed biquad filter configuration consisting of only two CFOAs, two resistors and two capacitors realizes all the standard types of the biquadratic filter functions at low-impedance output without any component matching conditions. The filter also provides orthogonal control of the natural angular frequency (ω<inf>0</inf>) and the bandwidth (BW). In addition, both proposed circuit configurations have good active and passive sensitivity performances. PSPICE simulations and experimental results based on commercially available AD844-type CFOAs are included, showing the excellent performance of the proposed configurations. © 2008 Elsevier Ltd. All rights reserved.
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Current-controlled quadrature oscillator using only CCCDBAs
(2009-12-01)
Sonjoi, Winyu
;
Tangsrirat, Worapong
;
Surakampontorn, Wanlop
An electronically tunable quadrature oscillator using only two current-controlled current differencing buffered amplifiers (CCCDBAs) and two grounded capacitors without external passive resistor is proposed. The outputs of two sinusoidal waveforms with 90° phase difference are available from the configuration. The oscillation condition and the oscillation frequency (ψ<inf>o</inf>) of the proposed oscillator circuit are tunable by electronically through controlling the external dc bias currents of the CCCDBAs. The simulation results with PSPICE are used to verify the theory.
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Insensitive current-tunable current-mode multifunction filter with minimum components using multi-output current followers
(2009-12-01)
Bunruang, Kritsada
;
Tangsrirat, Worapong
This paper describes a current-mode multifunction filter with a minimum number of active and passive elements using multi-output current followers (MO-CFs) as active elements. The proposed filter consists of only three MO-CFs and two grounded capacitors, which can simultaneously realize all the five standard biquadratic filter functions from the same configuration. The filter not only offers an independent electronic control of the natural angular frequency (ω<inf>o</inf>) and the quality factor (Q), but also provides the absence of the external passive resistors. Moreover, the parameter sensitivities are all very low.
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CMOS digitally controlled current follower and its application
(2009-12-01)
Prasertsom, Danucha
;
Tangsrirat, Worapong
A realization of the CMOS digitally controlled current follower (DC-CF) suitable for low-voltage high-frequency application is proposed. To achieve very low input resistance, it is realized using a modification of a low-input resistance stage as an input stage. To achieve the precise digital control of the current gain, the current division technique is used. The proposed DC-CF can operate with low voltage supplies of ±1.5 V, and is designed with 0.5- μm CMOS SCN05H process. As an application, the digitally programmable current-mode universal filter using the proposed DC-CF is given. Simulation results are also included.
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Current tunable current-mode biquadratic filter using dual-output current followers
(2009-12-01)
Bunruang, Kritsada
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Prasertsom, Danucha
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Pukkalanun, Tattaya
;
Tangsrirat, Worapong
This paper describes a current-mode multifunction filter with a minimum number of active and passive elements using dual-output current followers (DO-CFs) as active elements. By based on the dual-output current-controlled current conveyor (DO-CCCII)-based current followers, the proposed filter consists of only two DO-CFs and two grounded capacitor, without an external passive resistor requirement. The filter can realize all the standard biquadratic functions without changing the circuit configuration. Moreover, its natural angular frequency and bandwidth is controllable independently and electronically by adjusting an external bias current, and its active and passive sensitivities are low.
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Electronically tunable phase shifter using CDTAs
(2009-12-01)
Marungreang, Nattaphon
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Tanjaroen, Wason
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Pukkalanun, Tattaya
;
Tangsrirat, Worapong
The realization of an electronically tunable phase shifter using current differencing transconductance amplifiers (CDTAs) as active components is presented. The proposed filter employs only two CDTAs and one virtually grounded capacitor, which its phase shift can be electronically adjusted by varying the bias current of the CDTA. The circuit also exhibits high-output impedance, which is easy cascading in the current-mode operation. As application example, the current-mode biquad filter based on the proposed CDTA-based phase shifter circuit is also presented. PSPICE simulation results of the proposed circuit and its application are given to confirm the theoretical analysis.
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Resistorless current-mode quadrature sinusoidal oscillator using CDTAs
(2009-12-01)
Tanjaroen, Wason
;
Tangsrirat, Worapong
A circuit technique for realizing a current-mode quadrature sinusoidal oscillator using current differencing transconductance amplifiers (CDTAs) as active components is presented in this paper. The proposed circuit employing only three CDTAs and two grounded capacitors can provide two quadrature sinusoidal current outputs with 90° phase difference. The oscillation condition and the oscillation frequency (ω<inf>o</inf>) of the proposed circuit can be electronically and orthogonally tuned. Simulation results with PSPICE are used to confirm the presented theory.
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Cascadable current-mode filters using CDTAs
(2009-12-01)
Pongpisal, Tanin
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Unhavanich, Sumalee
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Tangsrirat, Worapong
;
Surakampontorn, Wanlop
In this paper, a variety of cascadable current-mode filter architectures incorporating current differencing transconductance amplifiers (CDTAs) and grounded passive elements are realized. The proposed filter topologies mainly contain the CDTA-based cascaded filter structure and the current feedback loop, which provides a systematic and structural method for realizing general filtering functions. They are convenient for integration, electronically tunable, easy cascadability, of low sensitivity, simple in structure and easy to design. Design examples and simulation results by PSPICE confirm the usefulness of the proposed approach.
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Current-mode multiphase sinusoidal oscillator using CDTA-based allpass sections
(2009-07-01)
Tangsrirat, Worapong
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Tanjaroen, Wason
;
Pukkalanun, Tattaya
In this work, a current tunable current-mode multiphase sinusoidal oscillator (MSO) employing current differencing transconductance amplifier (CDTA)-based first-order allpass sections is presented. The proposed MSO circuit, which uses only two CDTAs and one virtually grounded capacitor for each phase, can generate arbitrary 2 n-phase current-output signals (n = 2, 3, 4, ...) equally spaced in phase, all at high output impedance terminals. The oscillation condition and the oscillation frequency can be controlled electronically and independently by adjusting the bias current of the CDTA. The oscillator has low-sensitivity performance. Simulation results are also given to verify the functionality of the proposed oscillator. © 2008 Elsevier GmbH. All rights reserved.
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Digitally programmable current follower and its applications
(2009-05-01)
Tangsrirat, Worapong
;
Pukkalanun, Tattaya
In this paper, a CMOS implementation of the digitally programmable current follower (DP-CF) is presented. To achieve very low-input resistance, it is realized using a modification of a low-input resistance stage as an input stage. To achieve the precise digital control of the current gain, the current division technique is used. The proposed DP-CF is operated under ± 1.5 V voltage supplies, and designed with 0.5-μ m CMOS SCN05H process. Applications of the proposed DP-CF in realizing digitally programmable current-mode filter and rectifier are given. SPICE simulation results of the proposed circuit and its applications are also included. © 2008 Elsevier GmbH. All rights reserved.

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