Sumio Tsuiki

A general class of current-mode high-order OTA-C filters

A current-mode high-order filter configuration is introduced using multiple current output operational transconductance amplifiers OTAs. The circuit has been constructed by employing a current-mode integrator and a proportional block as basic building units. It is shown that the proposed circuit can realize a general class of high-order transfer functions. As an example, a fourth-order filter is given, together with simulated results by PSpice.

A Study on Pitch Detection of Sinusoidal Noise for Noise Reduction System

A noise reduction system based on an adaptive line enhancer (ALE) and noise estimation filter (NEF) has been proposed in order to reduce both wideband and sinusoidal noise in noisy speech. The noise reduction system has the ALE with less the computation load. However, the ALE needs a pitch detector of sinusoidal noise. In this paper, a pitch period detection using the tap coefficients of the ALE for estimating the sinusoidal noise is proposed. The proposed method can detect the pitch period of sinusoidal noise superposed on speech

Novel electronically tunable current-mode filter without external passive elements

This paper presents a current-mode filter with a general class of circuit transfer functions using active devices only. This circuit employs Operational Amplifiers (OAs) and multiple current output Operational Transconductance Amplifiers (OTAs) as the basic building units. It is shown that the circuit can realize various filter characteristics by choosing the current output branches. It is also shown that the circuit provides electronically tuning capability of the filter characteristics. An example is shown with the simulated results by PSpice.

A novel current-mode active-R biquad using differential-input differential-output operational amplifiers

This paper introduces a novel current-mode active-R biquadratic circuit employing two differential-input differential-output operational amplifiers (DIDO OAs). The circuit configuration has been obtained utilizing Soderstrands voltage-mode state variable filter as a prototype. It is shown that the proposed circuit can realize five different biquadratic transfer functions simultaneously without changing the circuit topology. The parasitic effects of DIDO OAs on the circuit characteristics are also discussed using a general model of OA gain. An example is given together with simulated results by PSpice.

A versatile current-mode biquad using operational amplifiers

A versatile current-mode biquadratic filter using three operational amplifiers and nine passive elements is proposed. By suitably choosing the output branch, lowpass, bandpass, highpass, bandstop and allpass transfer functions are realized simultaneously without changing the circuit configuration and elements. Two circuits, one is for low frequency application and the other for high frequency, are proposed. The center frequency, quality factor and gain constants of the circuit can be tuned independently. Simulated results show that the circuits work successfully.