Tuwanut, Panwit

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Tuwanut, Panwit
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Tuwanut, P.
Tuwanuti, Panwit
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panwit.tu@kmitl.ac.th

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    A simple circuit for sigma-delta /delta modulation
    (2005-12-01)
    Tuwanut, Panwit
    ;
    Maneechukate, Thongchai
    ;
    Koseeyapom, Jeerasuda
    ;
    Wardkein, Paramote
    This article represents a simple circuit which can function either as sigma-delta or delta modulation. The circuit is composed of three OTAs, a capacitor and two resistors which basically form Schmitt-trigger circuit. When input signal is present and fed to the inverting input node of OTA1, the circuit acts as a sigma-delta modulation. Contrarily, without adding any component, the same circuit functions as delta modulation when input signal is instead fed to a resister R<inf>1</inf> node, hi addition, frequency and amplitude of the modulated signal not only are independently adjusted but also these characteristics are electrical tuned. Based on the compactness of the proposed circuit, it is therefore suitable for IC realization. The computer simulation results are illustrated to confirm with the given circuit analysis. © 2005 IEEE.
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    Triangular-to-cosine wave technique based on exponential approximation
    (2001-12-01)
    Viboonsirikul, Piyamon
    ;
    Tuwanut, Panwit
    ;
    Wardkein, Paramote
    ;
    Maneechukate, Thongchai
    A novel approach for triangular-to-cosine wave approximation is presented The cosine wave is generated by the method of squaring the triangular wave and the passing through the exponential amplifier circuits. This approach is based on the Taylor's series for sinusoidal function. The superior point of this method to the existing ones is the simple circuit realization and low distortion cosine wave output Besides that, the proposed circuit can generate the square, triangular wave. The section of square wave and triangular wave generating uses relaxation oscillator with feeding back in current mode that produce the triangular and square wave in the same circuit. Furthermore, the squaring and exponential amplifier circuit can be configured based on another principle such as translinear in current mode which can be developed to suit IC implementation.
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    7 Decade low frequency switched capacitor oscillator
    (2001-12-01)
    Tuwanut, Panwit
    ;
    Wardkein, Paramote
    ;
    Maneechukate, Thongchai
    In this work a sine wave switched-capacitor (SC) oscillator based on feedback SC BPF oscillator is proposed. Advantage of this technique is high stability, constant amplitude at wide frequency range and suitable for amplitude control by output forced response technique. In addition, frequency tuning can be adjusted by clock control, which without effect to stability. The experimental results conforming the validity of the theory are also presented.
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    New analytic solution of second-order oscillator using multi-time variables technique
    (2005-01-01)
    Maneechukate, Thongchai
    ;
    Tuwanut, Panwit
    ;
    Koseeyaporn, Jeerasuda
    ;
    Wardkein, Paramote
    In this paper, a new analysis of sinusoidal oscillator amplitude controlled by forced response using the second order differential equation (ODE) is proposed. In general, the amplitude of the complete response is derived where forced response slope is normally assumed to be zero. The value of forced response only at initial time is thus employed to determine the amplitude. But if forced input is dynamic signal the amplitude of complete response gained by using such assumption is different from the experimental result. Thus, a new analysis of amplitude for a dynamic forced response is proposed in this paper. It is found that the forced response at any arbitrary time (not only at the initial time) is presented in a term of natural response magnitude. Magnitude of natural response is therefore directly controlled by forced response. To confirm the theoretical analysis, experimental results have been demonstrated and agreed well with the analysis results. © 2005 IEEE.