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OTA-based capacitance-to-period converter for capacitive sensors
(2013-03-28)
Kanjanapart, Naratorn
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Cheypoca, Thepjit
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Riewruja, Vanchai
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Petchmaneelumka, Wandee
A simple design technique for realization of a capacitance-to-period converter based on operational transconductance amplifiers (OTAs) is presented in this paper. The proposed principle utilizes the behavior of astable multivibrator. The configuration of converter is implemented using commercial available and low cost devices. The obtained time period is proportional to sensing capacitance. The conversion gain of proposed scheme can be changed by electronic means. Circuit performances verified by experimental results are agreed with the expected values. © 2013 ICIC International.
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OTA-based electronically variable floating inductance simulator
(2011-12-01)
Longsomboon, Kittisak
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Petchmaneelumka, Wandee
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Cheypoca, Thepjit
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Riewruja, Vanchai
A circuit technique to implement a floating inductance simulator using operational transconductance amplifiers (OTAs) is introduced in this paper. The realization method based on the commercially available OTA, one resistor and one capacitor provides the advantage of an electronic adjusting capability. The resulting inductance can be electronically varied by tuning the external bias current of OTA. The obtained simulator is also applied in system response compensation. Experimental results verifying the circuit performances are included. © 2011 ICROS.
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Electronically adjustable PD controller using OTAs
(2011-01-01)
Petchmaneelumka, Wandee
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Cheypoca, Thepjit
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Riewruja, Vanchai
A method for realizing the PD controller is presented in this paper. The circuit implementation is based on operational transconductance amplifiers (OTAs) as active elements with a grounded capacitor. The proportional gain and derivative time can be electronically varied by tuning the external bias current of OTA. Moreover, the structure of the proposed scheme can be simply realized the PID controller by including resistor-capacitor series network at the output terminal. Experimental results verifying the performances of the proposed circuit are in close agreement with the theoretical values. © 2011 SICE.
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Electronically adjustable phase shifter using OTAs
(2010-12-01)
Songsuwankit, Kanoknuch
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Petchmaneelumka, Wandee
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Riewruja, Vanchai
First-order phase shifter using operational transconductance amplifiers (OTAs) as active elements is presented in this paper. The corner frequency of the proposed phase shifter can be adjusted by electronic means. The purpose of this paper is emphasized on simple configuration and low cost. The phase response between input and output signals against the operating frequency is varied from 180 to 0 degrees of phase lead. The principle of the proposed circuit is confirmed by simulation and experimental results. To verify the proposed circuit performance, the sinusoidal oscillator is provided for circuit application. ©ICROS.
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OTA-based floating inductance simulator
(2009-12-01)
Koomgaew, Chitpol
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Petchmaneelumka, Wandee
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Riewruja, Vanchai
A simple circuit technique to realise a floating inductance simulator for system response compensation is presented in this paper. The circuit implementation is based on the use of the operational transconductance amplifiers (OTAs) as active elements. The proposed circuit converts a grounded capacitance into a floating inductance with electronically variable properties. The proposed inductor is attractive in terms of simple configuration and low cost. Experimental results verifying the performances of the proposed circuit are also included. © 2009 SICE.
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A novel resolver-to-DC converter based on OTA-based inverse-sine function circuit
(2008-12-01)
Kaewpoonsuk, Anucha
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Petchmaneelumka, Wandee
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Rerkratn, Apinai
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Tammaruckwattana, Sirichai
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Riewruja, Vanchai
A new technique for realizing the resolver-to-DC converter using the OTA-based inverse-sine function circuit is presented. The proposed converter comprises the demodulator, absolute detector, minimum detector, ± unity-gain amplifier, controlled signal logic circuit, and OTA-based inverse-sine function circuit. The output voltage is linearly proportional to the resolver angle with maximum absolute error of about 0.195%, which is less than the error from the conventional resolver-to-DC converter based on the similar OTA-based inverse-sine function circuit. PSPICE simulation and experimental results verifying the performances of the proposed circuit are in close agreement with the expected values. © 2008 SICE.
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OTA-based electronically adjustable floating positive/negative resistor
(2008-12-01)
Petchmaneelumka, Wandee
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Kamsri, Thawatchai
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Wangwiwatthana, Chaleampan
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Riewruja, Vanchai
This paper presents a method to realize an operational transconductance amplifier (OTA) based adjustable floating resistor. The magnitude of the resulting resistance can be electrically varied by changing the external bias currents of OTAs. The proposed resistor is based on an active network termed "dual-output voltage-to-current (DO-V/I) converter", which is the OTA-based voltage-to-current converter with electronically variable property. The realization method provides both a positive and a negative resistance using the same scheme. The proposed design is attractive in the terms of simple configuration and low cost. Experimental results showing the circuit performance based on the use of the commercially available OTAs are included. © 2008 SICE.
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Positive/negative floating resistor using OTAs
(2008-12-01)
Petchmaneelumka, Wandee
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Julsereewong, Prasit
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Riewruja, Vanchai
A method for realizing a floating resistor based on operational transconductanee amplifiers (OTAs) is presented in this paper. The proposed design is composed of only OTAs without any external resistor. The magnitude of the obtained resistance is electronically varied by adjusting the external bias currents of OTAs. Both a positive and a negative resistance can be achieved in the same circuit. The proposed scheme provides the simple configuration and low cost. The circuit performances based on the use of the commercially available OTAs are confirmed by the experimental results.
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Floating current-controlled resistance converters using OTAs
(2008-11-01)
Riewruja, Vanchai
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Petchmaneelumka, Wandee
A simple configuration to realize the floating resistance converters using operational transconductance amplifiers (OTAs) is introduced in this paper. Negative and positive resistances driven by both the voltage and current signals can be achieved in the same scheme. The magnitude of the resulting resistances can be electronically controlled by varying the bias current ratio of OTAs. In addition, the capacitance conversion can be also provided without stability problem. Experimental results verifying the performances of the proposed converters are presented. © 2007 Elsevier GmbH. All rights reserved.
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OTA-based sine-to-triangular wave converter
(2006-12-01)
Riewruja, Vanchai
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Kaewpoonsuk, Anucha
A sine-to-triangular wave converter based on operational transconductance amplifiers (OTAs) is proposed in this paper. The realization method exploits a hyperbolic tangent behavior of an OTA to convert from a sine wave to a triangular wave. The proposed circuit provides a simple configuration and employs only OTAs as the active elements. This scheme can be operated in both a voltage-controlled mode and a current-controlled mode. The performances of the proposed circuit are discussed in detail and confirmed by the experimental results. © Birkhauser Boston 2006.

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