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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
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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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A novel widely linear current-tunable CMOS transconductor
(2009-12-01)
Kaewdang, Khanittha
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Surakampontorn, Wanlop
A CMOS-based linearly tunable transconductor is proposed in this paper. The realization technique is achieved by using a fully differential transconductor and a current variable gain stage, for a power supply of ±1.5V. Its transconductance gain can be linearly tuned by an external bias current for more than 4 decades. The transconductor cell is designed in 0.5μm AMIS technology. The performance of the proposed circuit is discussed and confirmed through PSPICE simulation results. ©2009 IEEE.
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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
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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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A translinear-based true RMS-to-DC converter using only npn BJTs
(2009-06-01)
Kaewdang, Khanittha
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Kumwachara, Kiattisak
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Surakampontorn, Wanlop
A true rms-to-dc converter based on the explicit computation technique is proposed in this paper. Since the scheme utilizes translinear principle circuits to realize current-mode squarer, averaging and square root circuits, only npn bipolar junction transistors are required. The conversion circuit has wide-band frequency response and can be operated with single supply voltage at 2 V. PSPICE simulation and experimental results show good agreement with the theoretical predictions. © 2008 Elsevier GmbH. All rights reserved.
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Low-voltage digitally controlled current differencing buffered amplifier and its application
(2009-04-03)
Tangsrirat, Worapong
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Prasertsom, Danucha
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Surakampontorn, Wanlop
In this paper, a design of a low-voltage digitally controlled current differencing buffered amplifier (DC-CDBA) is introduced. The realization scheme is through the cascade connection of a current differencing circuit, a current division network (CDN) and a buffered voltage amplifier. To achieve the digital control of the current gain of the circuit, a novel CDN is also proposed. The proposed DC-CDBA can operate with the low supply voltage of ± 1.25 V. PSPICE simulations using standard 0.5 - μ m CMOS process parameters are in agreement with the theory. An application example using the proposed DC-CDBAs as active elements in the realization of the digitally tuned current-mode universal filter is also included. © 2008 Elsevier GmbH. All rights reserved.
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Voltage-mode threshold-independent analogue multiplier
(2009-05-01)
Boonchu, Boonchai
;
Surakampontorn, Wanlop
In this article, a new threshold-independent four-quadrant analogue multiplier is designed and developed. It is based on the square-law of the MOS transistor in the saturation region and quarter-square algebraic identity. The circuit structure uses voltage summing and voltage-mode squaring stages. By applying the reference voltage to the voltage summing stage, the threshold-independent multiplication function can be achieved. On the basis of the voltage-mode circuit structure, the proposed multiplier produces an output signal in voltage form without resistors. The performances of the proposed circuit have been simulated with PSPICE. Simulation results show that the multiplier has a wide band capability, where a-3dB bandwidth of 160MHz is achieved. The circuit has 0.75% linearity error and 0.47% total harmonic distortion under the maximum input voltage of 500mV at both multiplier inputs. The power consumption is about 0.5mW with a1.5V power supply voltage. To verify the performances of the proposed multiplier, experimental results with discrete transistor arrays are obtained. The results will be useful in analogue signal processing applications.
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Double-capacitor technique for wide frequency range phase compensation in G m-C and MOSFET-C filters
(2009-01-01)
Khumsat, Phanumas
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Worapishet, Apisak
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Surakampontorn, Wanlop
A double-capacitor phase error compensation configuration is proposed for G <inf>m</inf>-C and MOSFET-C filters. The use of two capacitors enables the effective compensation capacitance to track with the tuning resistance, thereby making it more effective over a wider frequency tuning range as compared to the conventional single-capacitor configuration. Simulations of 5th-order Chebyshev filters in a 0.18 μm CMOS process with more than one octave tuning range were carried out to demonstrate the viability of the proposed double-capacitor configuration for both G <inf>m</inf>-C and MOSFET-C filters. Copyright © 2009 The Institute of Electronics, Information and Communication Engineers.
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Low-voltage digitally controlled current differencing buffered amplifier
(2008-12-01)
Prasertsom, Danucha
;
Tangsrirat, Worapong
;
Surakampontorn, Wanlop
A low-voltage digitally controlled current differencing buffered amplifier (DC-CDBA) is proposed. The realization scheme is through the cascade connection of a current differencing circuit, a current division network (CDN) and a buffered voltage amplifier. To achieve the digital control of the current gain of the circuit, a novel CDN is also proposed. The proposed DC-CDBA can operate with the low supply voltage of ±1.25V. PSPICE simulations using standard 0.5μ CMOS process parameters are in agreement with the theory. © 2008 IEEE.
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Temperature-insensitive current-mode square-rooting circuit using only two CDTAs
(2008-12-01)
Mongkolwai, Pratya
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Prasertsom, Danucha
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Tangsrirat, Worapong
;
Surakampontorn, Wanlop
A simple circuit configuration of the temperature- insensitive current-mode square-rooting circuit using current differencing transconductance amplifiers (CDTAs) as active components is described. It has been designed by using only two CDTAs without the use of external passive elements. The current gain of the proposed circuit can be adjusted electronically by an external bias current, thanks to the tunability property of the CDTA. PSPICE simulation results are employed to confirm the theoretical analysis. © 2008 IEEE.

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