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In this paper, a new universal current-mode filtering circuit with single input and multi-outputs based on OTAs (operational transconductance amplifiers) is proposed. The circuit just consists of two operational transconductance amplifiers, one current controlled current amplifier with multi-outputs (MO-CCCA), and two grounded capacitors. It can realize low-pass, band-pass, high-pass, band-stop, and all-pass filters simultaneously. Its quality factor and natural frequency can be tuned independently and the sensitivities are very low. Moreover, the non-ideal characteristic of the proposed filter is analysed and simulated by PSPICE. [ABSTRACT FROM AUTHOR]

In this paper, a new current differencing cascaded transconductance amplifier (CDCTA) is presented. The CDCTA circuit consists of a current differencing unit and n cascaded highly linear voltage-controlled transconductance amplifiers, and it possesses wide bandwidth and lineartunable feature. Based on this CDCTA, a systematic design method generating current-mode (CM) multiple-loop feedback filter is proposed. By altering the parameters of the design matrix, multiple nth-order CM all-pole low pass filters structures can be synthesized without changing internal circuit. The nth-order filters have low complexity and meet the requirement of no active and passive element matching conditions as adopting only a single CDCTA and n grounded capacitors. Furthermore, the frequency of the nth-order filters can be linearly tuned by the bias voltage. A fourth-order Butterworth filter is designed as an example, and its Cadence simulation results have good agreement with the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this paper, a new fourth-order complex (polyphase) filter is realized with the leapfrog structure. The proposed filter is based on the first-order stage using multi-output current differencing transconductance amplifiers (MOCDTAs). The design procedures for the realization of the first-order stage and fourth-order leapfrog polyphase filter are presented. In the procedures, the signal flow diagrams are also presented. The proposed design using MOCDTA simplifies the circuit of the current-mode leapfrog complex filter, where there are no resistors and with minimum number of active components. Besides, its centre frequency and bandwidth could be electrically tunable independently. The centre frequency of the proposed filter could be adjusted from 20 to 80 MHz, and its bandwidth could be more than 20 MHz. With ± 1.25 V supply, two examples of the proposed filter are introduced. Their bandwidths are from 46.1 to 68.5 MHz and from 22.3 to 48.4 MHz, respectively. Their image rejection ratios could be more than 59 and 39 dB, respectively. Meanwhile, both the IIP3s are over 18 dBm. The theoretical results are demonstrated by using SPECTRE simulation in CHRT 0.18 μm standard complementary metal oxide semiconductor (CMOS) process. [ABSTRACT FROM PUBLISHER]

In this paper, a NMOS-based wideband low power and linear tunable transconductance current differencing transconductance amplifier (CDTA) is presented. Based on the NMOS CDTA, a novel simple and easily reconfigurable configurable analogue block (CAB) is designed. Moreover, using the novel CAB, a simple and versatile butterfly-shaped FPAA structure is introduced. The FPAA consists of six identical CABs, and it could realize six order current-mode low pass filter, second order current-mode universal filter, current-mode quadrature oscillator, current-mode multi-phase oscillator and current-mode multiplier for analog signal processing. The Cadence IC Design Tools 5.1.41 post-layout simulation and measurement results are included to confirm the theory. [ABSTRACT FROM AUTHOR]

In this paper, a new active device, current differencing cascaded transconductance amplifier (CDCTA), has been presented. The proposed CDCTA simplifies the design of the current-mode filter circuit considerably, especially the design of high-order filter. Moreover, a current-mode nth-order filter based on the CDCTA is proposed in the paper. The proposed circuit, which adopts only an active component and n grounded capacitors, contains minimal active component and passive one. It enjoys the simple configuration and is suitable for integrated circuit (IC) fabrication. PSpice simulations for current-mode third-order filter based on this structure have also been conducted, and the results are in good agreement with the theoretical analysis. The influences of the CDCTA non-idealities are also discussed. [ABSTRACT FROM AUTHOR]