This article presents the new current-mode counterclockwise (CCW) and clockwise (CW) Schmitt triggers based on multiple-output current controlled current differencing transconductance amplifier (MO-CCCDTA). The circuit descriptions are very simple, each construction consists of only single MO-CCCDTA, without any external passive element. The hysteresis and amplitude of the output current of each Schmitt trigger can be tuned independently/ electronically by input bias currents. In addition, the output signals are independent of the thermal voltage (V T ). The applications as a relaxation oscillator, triangular/square wave generator, pulse width modulation and monostable multivibrator are given here to display the usefulnesses of the presented Schmitt triggers. The PSpice simulation and experimental results are depicted, and agree well with the theoretical anticipation. The maximum power consumptions of CCW and CW Schmitt triggers are approximately 235 and 191 lW, respectively, at ±1.5 V supply voltages.
This paper presents the design of a voltage-mode three-input single-output multifunction first-order filter employing commercially available LT1228 IC for easy verification of the proposed circuit by laboratory measurements. The proposed filter is very simple, consisting of a single LT1228 as an active device with two resistors and one capacitor. The output voltage node is low impedance, resulting in an easy cascade-ability with other voltage-mode configurations. The proposed filter provides four filter responses: low-pass filter (LP), high-pass filter (HP), inverting all-pass filter (AP−), and non-inverting all-pass filter (AP+) in the same circuit configuration. The selection of output filter responses can be conducted without additional inverting or double gains, which is easy to be controlled by the digital method. The control of pole frequency and phase response can be conducted electronically through the bias current (IB). The matching condition during tuning the phase response with constant voltage gain is not required. Moreover, the pass-band voltage gain of the LP and HP functions can be controlled by adjusting the value of resistors without affecting the pole frequency and phase response. Additionally, the phase responses of the AP filters can be selected as both lagging or leading phase responses. The parasitic effects on the filtering performances were also analyzed and studied. The performances of the proposed filter were simulated and experimented with a ±5 V voltage supply. For the AP+ experimental result, the leading phase response for 1 kHz to 1 MHz frequency changed from 180 to 0 degrees. For the AP− experimental result, the lagging phase response for 1 kHz to 1 MHz frequency changed from 0 to −180 degrees. The design of the quadrature oscillator based on the proposed first-order filter is also included as an application example.
Abstract-This article presents a basic current-mode building block for analog signal processing, namely current conveyor transconductance amplifier (CCTA) using the commercially available ICs. The performances are examined through PSPICE simulations and experiment, displaying usabilities of the new active element. The description includes some examples as a voltage-mode universal biquad filter, a grounded inductance, a current-mode multiplier and oscillator. They occupy only a single CCTA.
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