This paper presents frequency agile filters based on current difference transconductance amplifier (CDTA) and voltage difference transconductance amplifier (VDTA). The proposed agile filter configurations employ grounded passive components and hence are suitable for integration. Extensive SPICE simulations using 0.25？μm TSMC CMOS technology model parameters are carried out for functional verification. The proposed configurations are compared in terms of performance parameters such as power dissipation, signal to noise ratio (SNR), and maximum output noise voltage. 1. Introduction The rapid evolution of wireless services has led to demand for one-fits-all “analog” front end solution. These services use different standards and therefore necessitate development of integrated multistandard transceivers as they result in reduction of size, price, complexity, and power consumption. The parameters of integrated transceiver can be modified in order to be able to adapt to the specifications of each standard [1]. Practically, the designs employ either elements handling various standards in parallel or reconfigurable elements. The frequency agile filter (FAF) [1–10] characterized by adjustment range, reconfigurability, and agility may be used in transceivers. The term shadow filters is sometimes used in literature to refer to FAF [11, 12]. The literature survey shows that a limited number of topologies of active FAF are available and are based on op-amp [1] and current mode active block [2, 3] and CMOS [4]. There is a wide range of current mode building blocks available in open literature. Among these blocks current difference transconductance amplifier (CDTA) [11] is most suitable for current mode signal processing owing to its low input and high output impedances, respectively. The VDTA is yet another recently introduced building block which works on a principle similar to that of CDTA except that the input current differencing unit is replaced by the voltage differencing circuit. Many applications such as filters and oscillators based on CDTA and VDTA are available and have been reported in the literature [13–27] and references cited therein. The main intention of this paper is to present CDTA and VDTA based frequency agile filter topologies. The proposed filters are suitable for integration as these employ grounded capacitors and a resistor. The paper is organised as follows. The FAF implementation scheme is briefly reviewed in Section 2. The CDTA based Class 0, Class 1, and Class 2 FAF are presented in Section 3. Section 4 deals with the realization of VDTA
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