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Author: search.filters.author.Fujii, Nobuo

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    Two new RC oscillators using CCIIs
    (2005-12-01)
    Fongsamut, Chalermpan
    ;
    Fujii, Nobuo
    ;
    Surakampontorn, Wanlop
    Two new sinusoidal oscillator circuits using current conveyors are presented in this paper. The two oscillators are related to each other by the RC:CR transformation. Each oscillator consists of two positive second-generation current conveyors (CCII+) and the minimum of (four) passive elements, two capacitors and two resistors. One of the oscillators can be realized by employing grounded capacitors and is desirable for VLSI realization. The passive and active sensitivities of all circuits are quite low. The SPICE simulation and experimental works are performed to verify this theoretical prediction. © 2005 IEEE.
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    A design of CMOS tunable current amplifiers
    (2004-12-01)
    Kaewdang, Khanittha
    ;
    Surakampontom, Wanlop
    ;
    Fujii, Nobuo
    Two CMOS tunable current amplifiers are proposed in this paper. They are voltage-controlled current gain and current-controlled current gain. Both circuits are designed based on CMOS OTA which amplifiers are linearly tunable. The circuits achieve their linearity by squaring the nonlinear transconductance of the balanced CMOS OTA. The proposed voltage-controlled current amplifier can be linearly tuned by DC voltage. The amplifier's nonlinearity is less than 1% for the voltage control (V<inf>c</inf>) range from -2V to 2V. The current-controlled current amplifier can also have a linearly-tunable current gain by DC bias current over three decades (0.1-20) with an error less than 1.5%. The performances of the proposed circuit are discussed and confirmed through PSPICE simulation.
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    Realization of leapfrog filters using current differential buffered amplifiers
    (2003-01-01)
    Tangsrirat, Worapong
    ;
    Surakampontorn, Wanlop
    ;
    Fujii, Nobuo
    In this paper, is shown an approach to realize leapfrog structures obtained from proto-type passive RLC ladder filters using current differencing buffered amplifiers (CDBA) as active elements. The use of the CDBA's provides advantages that the realization procedure is simplified and the number of active components required is reduced. The approach is quite suitable for the realization of band-pass ladder filters, which generally requires a complicated structure to simulate LC series and/or parallel resonant branches by the conventional opamp-based leapfrog filters. A simple circuit configuration of the CDBA suitable for high frequency and low power supply voltage applications is also presented. As design examples, a fifth-order Butterworth low-pass ladder filter and a sixth-order Chebyshev bandpass ladder filter are designed. The effectiveness and the correctness of the proposed approach and the characteristics of the proposed filters are verified and examined through computer simulation.
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    Current-mode leapfrog ladder filters using CDBAs
    (2002-01-01)
    Tangsrirat, Worapong
    ;
    Fujii, Nobuo
    ;
    Surakampontorn, Wanlop
    In this paper, a possible realization of a current differencing buffered amplifier (CDBA) in the low-voltage operation is proposed. A leapfrog simulation of the current-mode ladder network using the CDBA as active circuit building blocks is then introduced. In order to demonstrate that the CDBA considerably simplifies the leapfrog structure of the current-mode ladder filters, a fifth-order Butterworth low-pass filter and a sixth-order Chebyshev bandpass filter which require a minimum of active components will be presented. PSPICE simulation results are employed to verify the correctness of the realization procedure.
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    Low-voltage current mode power factor function generator
    (2000-01-01)
    Kumwachara, Kiattisak
    ;
    Fujii, Nobuo
    This paper proposes a realization of power factor function generator having an arbitrary base and power factor which are determined by the ratios of the currents provided from outside of the circuit. The circuit characteristics do not depend on any transistor parameters, temperature, and other environmental conditions. The circuit operation is based on current mode that has a capability of low power supply voltage operation below than 2.0V. SPICE simulation has been carried out using 0.7 μm BiCMOS parameters and shows quite good transfer characteristics.
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    Low voltage bipolar translinear-based temperature dependent current source and its application
    (1998-12-01)
    Kumwachara, Kiattisak
    ;
    Fujii, Nobuo
    ;
    Surakampontorn, Wanlop
    An integrable low voltage bipolar translinear-based temperature dependent current source is presented. The circuit operation is in the current mode, and the output current is directly proportional to temperature and can be varied by external currents. The circuit can operate with a low DC single power supply voltage of 2.0 volts. The circuit is applied to a first-order low-pass filter which is based on a bipolar current mirror. The SPICE simulation shows quite good performance of temperature compensation.