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Author: search.filters.author.Manositthichai, NarongsakSubject: search.filters.subject.Tunable

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    High-order bp filter using biquad log-domain method
    (2018-07-02)
    Wongprommoon, Natapong
    ;
    Manositthichai, Narongsak
    ;
    Prommee, Pipat
    High-order band-pass ladder filter based on Log-domain biquad functions is presented in this paper. High-order ladder filter is designed from RLC ladder filter prototype based on two types of biquad log-domain filters. Log-domain lossy and lossless integrator concepts are used to realize biquad log-domain filter in each type. Log-domain lossy integrator is easily realized by using 7 transistors and 1 grounded capacitor and log-domain lossless integrator is also easily realized by using log-domain lossy integrator by adding feedback to the input which consists of 8 transistors and 1 grounded capacitor. By adjusting bias current the frequency responses the filter can be obtain between 100 kHz and 100 MHz. This filter operates in transistor level which is suitable for operating in high frequency operation. A commercial array BJT technology is used in PSpice simulation.
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    Active-only variable-gain low-pass filter for dual-mode multiphase sinusoidal oscillator application
    (2017-01-01)
    Prommee, Pipat
    ;
    Manositthichai, Narongsak
    ;
    Khateb, Fabian
    This research presents an active-only low-pass (LP) filter whose pole frequency and gain are independently tunable by means of bias current manipulation. The realization of the proposed LP filter required one operational amplifier, two operational transconductance amplifiers, and two MOS transistors. The multiphase sinusoidal oscillator (MSO) was subsequently realized by cascading n LP filters (n = 3) and loop-backing the output of the last LP filter to the input of the first LP filter. Simulations were carried out and the results revealed that the MSO could simultaneously achieve low impedance voltage and high impedance current outputs without the circuit topology alteration. The frequency of oscillation and the condition of oscillation could also be electronically tuned without disturbing each other. Furthermore, the sinusoidal signal of the MSO exhibited relatively low total harmonic distortion of about 0.8% at 2.75 MHz. To verify, a prototype of the active-only LP-based MSO (n = 3) was constructed and experiments were performed. The experimental findings were agreeable with the simulation results.