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This paper presents two new current differencing transconductance amplifiers (CDTAs)-based electronically tunable current-mode four-phase quadrature oscillators (QO). The proposed QOs consist of two CDTAs, one resistor and two grounded capacitors, respectively, which are suitable for monolithic integration. The condition of oscillation (CO) and frequency of oscillation (FO) can be independently controlled, and the FO can be electronically tunable by adjusting the bias current of the CDTA. Moreover, the QOs can provide four quadrature output currents at high-output-impedance nodes, which enable the QOs can be connected directly to the next stage without any impedance matching requirements. Cadence IC Design Tools 5.1.41 (Cadence Design Systems Inc., San Jose, CA) post-layout simulation results and experimental evidence are included to confirm the theory. [ABSTRACT FROM PUBLISHER]

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]