Two new configurations for voltage mode universal filters (VMUFs) using only two current differencing buffered amplifiers (CDBAs) are proposed. Both of the new configurations can realize all the five standard types of the filters, namely, low pass (LP), high pass (HP), band pass (BP), band stop (BS), and all pass (AP), from the same topology. In contrast to previously known CDBA-based VMUFs, the new configurations do not need an additional active device for voltage inversion to realize all pass functions. The proposed configurations offer the tunability of the natural angular frequency , quality factor , or the bandwidth (BW) through separate virtually grounded resistors. Moreover, both circuits have resistive input impedance (which can be made high) and a low output impedance to facilitate easy cascading without additional buffers. PSPICE simulation results, based upon commercially available AD844 ICs to implement the CDBA, are included which confirm the practical workability of the new VMUF configurations. 1. Introduction Analog filters are widely used for continuous-time signal processing in communication, measurement, instrumentation, and control systems [1]. Universal biquadratic filters are particularly attractive since they can realize all the five standard types of the filters, namely, low pass (LP), high pass (HP), band pass (BP), band stop (BS), and all pass (AP), from the same topology. Whereas universal voltage mode filters using current conveyors (CCs) or current feedback operational amplifiers (CFOAs) have received considerable attention in the technical literature, many of the reported circuits suffer from the drawbacks of requiring a large number of active and/or passive components and/or nonavailability of tuning of filter parameters [2]. Traditionally, the analog signal processing operations have been accomplished employing the voltage as signal variable. On the other hand, it has also been recognized that current mode circuits can achieve significant improvement in bandwidth, simplification of circuitry, power consumption, and dynamic range [3]. In order to maintain compatibility with existing voltage processing circuits as well as taking advantages of current mode circuits, a new active element called current differencing buffered amplifier (CDBA) was introduced in [4]. CDBA is suitable for IC implementation in both bipolar and CMOS technologies [4, 5]. Since a CDBA operates in both current mode and voltage mode, along with current differencing feature, CDBA has been shown to offer a lot of flexibility in circuit design; for
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