Abstract:
A four-inputs and two-outputs voltage-mode universal biquadratic filter using only two operational transconductance amplifiers (OTAs) and two capacitors is presented. The new circuits offer several advantages, such as employing the minimum number of active and passive components (two OTAs and two capacitors); the versatility to synthesize highpass, bandpass, lowpass, notch and allpass responses; high input impedance and employing only grounded capacitors for bandpass and lowpass filter realizations; some derived filter types enjoy the availability of one more simultaneously output filter response and good sensitivities performance

Abstract:
This paper presents a new current mode (CM) single-input and multi-output (SIMO)-type biquad using two multiple output OTAs and one current follower as an active device and having two grounded capacitors. This SIMO type circuit realizes all the five filter functions as low pass, band pass, high pass, band reject and all pass filter transfer functions simultaneously. This circuit has the unity gain transfer function for all the five types of filters. The circuit enjoys electronic tunability of angular frequency and bandwidth. The 0.18 μm TSMC technology process parameters have been utilized to test and verify the performance characteristics of the circuit using PSPICE. The sensitivity analysis, transient response and calculations of total harmonic distortion have also been shown.

Abstract:
A universal filter with dual-output current follower (DO-CF), two transconductance amplifiers (OTAs) and two passive elements is presented in this paper. The filter is tunable, of the single-input multiple-output (SIMO) type, and operates in the current mode. Our solution utilizes a low-impedance input node and high-impedance outputs. All types of the active elements used can be realized using our UCC-N1B 0520 integrated circuit and therefore the paper contains not only simulation results that were obtained with the help of behavioral model of the UCC-N1B 0520 element, but also the characteristics that were gained by measurement with the mentioned circuit. The presented simulation and measurement results prove the quality of designed filter. Similar multi-loop structures are very-well known, but there are some drawbacks that are not discussed in similar papers. This paper also contains detailed study of parasitic influences on the filter performance.

Abstract:
This paper proposes a multi-input single-output (MISO) third order voltage mode (VM) universal filter using only one operational transresistance amplifier (OTRA). The proposed circuit realizes low-pass, high-pass, all-pass, band-pass, and notch responses from the same topology. The PSPICE Simulation results using 0.5？μm CMOS technology agree well with the theoretical design. 1. Introduction Operational transresistance amplifier (OTRA) has emerged as an alternate current mode analog building block [1, 2] since it inherits all the advantages offered by other current mode building blocks such as current conveyor (CC) [3–6], operational transconductance amplifier (OTA) [7], current differencing buffered amplifier (CDBA) [8], differential voltage current conveyor (DVCC) [9]. The input terminals of OTRA are internally grounded, thereby eliminating parasitic capacitances at the input. OTRA has the advantages of a high slew rate and wide bandwidth. It is a high-gain current input voltage output device. Some analog filters using OTRA have been reported in [10–16] and references cited there in. It is well known that higher order analog filters using different kinds of active elements are of considerable interest, as they may be used for some special applications where sharp cut off is desirable and at the same time also useful to implement digital filters. Higher order filters can be obtained by various methods such as cascading lower order filter or state variable method or signal flow graph. Although OTRA based third order filters are reported in the literature [17–19], they all involve more that one OTRA. In this work an attempt is made to propose a third order voltage mode (VM) universal filter employing single OTRA as an active element. All of the five filters, namely lowpass (LPF), highpass (HPF), allpass (APF), bandpass (BPF), notch (NF), can be obtained from the same topology. 2. Circuit Description The circuit symbol of an OTRA is illustrated in Figure 1. The characteristic equations of this element can be described as A CMOS-based OTRA using 0.5？μm CMOS technology is given in Figure 2 [2]. Figure 1: Block diagram of OTRA. Figure 2: Internal circuit of OTRA [ 2]. A generalized th order filter topology using single OTRA is shown in Figure 3 [20]. The routine analysis gives a voltage transfer function as The proposed third order universal filter is obtained from Figure 3, if one considers , , , and splits the terminal into three parts and terminal into two parts as shown in Figure 4. Figure 3: Generalized nth order filter. Figure 4: Proposed third order

Abstract:
A new universal tunable high-order OTA-C filter based on a signal-flow-graph realization of the transfer function is designed. The filter needs only OTAs and grounded capacitors, and it is convenient for realization with MOS technology. Experimental results are given to show its feasibility.

Abstract:
A new multi-function high-order current-driven filter is proposed. The filter uses only operational amplifiers, and operational transconductance amplifiers (OTAs). Without using any external passive elements, a variety of high-order input-current/output-current and/or input-current/output-voltage responses can be realised without changing the circuit topology and without any matching or cancellation conditions. The parameters of the high-order filter responses can be electronically tuned by adjusting the bias currents of the OTAs.

Abstract:
It is presented a method to design Current-Mode (CM) filters from the transformation of the well-known Voltage-Mode (VM) opamp-RC filters. First, it is shown the simulation of a low-frequency opamp-RC filter with stable high Q, by applying the Y-Δ transformation. Second, it is described the transformation of the VM opamp-RC filter to a VM Gm-C filter and the symbolic transfer functions of the VM Gm-C filter are derived. Third, it is shown the transformation of the VM Gm-C filter to a CM Gm-C filter and the symbolic transfer functions of the CM filter are derived to show that both, the VM and the CM Gm-C filters perform the same behavior. Finally, some guidelines are introduced to design CM filters with CMOS OTAs and current conveyors.

Abstract:
This paper introduces a novel voltage-mode multifunction biquadratic filter with single input and four outputs using two plus-type differential difference current conveyors (DDCCs) and four grounded passive components. The filter can realize inverting highpass, inverting bandpass, noninverting lowpass, and noninverting bandpass filter responses, simultaneously. It still maintains the following advantages: (i) using grounded capacitors attractive for integration and absorbing shunt parasitic capacitance, (ii) using grounded resistors at all terminals of DDCCs suitable for the variations of filter parameters and absorbing series parasitic resistances at all terminals of DDCCs, (iii) high-input impedance good for cascadability, (iv) no need to change the filter topology, (v) no need to component-matching conditions, (vi) low active and passive sensitivity performances, and (vii) simpler configuration due to the use of plus-type DDCCs only. HSPICE and MATLAB simulations results are provided to demonstrate the theoretical analysis. 1. Introduction As a current-mode active device, the differential difference current conveyor (DDCC) has the advantages of both the second-generation current conveyor (CCII) (such as large signal bandwidth, great linearity, wide dynamic range) and the differential difference amplifier (DDA) (such as high-input impedance and arithmetic operation capability) [1]. This element is a versatile building block whose applications exist in the literature [1–7]. Voltage-mode active filters with high-input impedance are of great interest because several cells of this kind can be directly connected for implementing higher-order filters [3–11]. In 2003, Chang and Chen proposed a universal voltage-mode filter with three inputs and a single output [2]. The circuit can realize all five different generic filtering responses but only highpass and bandpass responses have the advantage of high-input impedance. In 2004, Horng et al. proposed a multifunction filter with a single input and three outputs [3]. The circuit can realize highpass, bandpass, and lowpass responses, simultaneously. However, it is based on two minus-type DDCCs. In 2005, Ibrahim et al. proposed two single DDCC biquads with high-input impedance and minimum number of passive elements [4]. The highpass, bandpass, or lowpass filter responses cannot be realized in the same configuration. In 2007, Chiu and Horng proposed a universal voltage-mode filter with three inputs and a single output [5]. The circuit has high-input and low-output impedance advantages but it uses three plus-type

Abstract:
This article presents an active-only current-mode universal biquad filter performing three standard functions: low-pass, high-pass and band-pass function, which can be readily modified to achieve the rest functions (band-stop and all-pass). The circuit principle is based on active-only circuit designed by using differentiators which are constructed from current controlled current conveyor transconductance amplifier (CCCCTA) cooperating with an internally frequency compensated operational amplifier (OA). The features of the circuit are that: the pole frequency and quality factor can be independently tuned via the input bias currents and it is ideally temperature-insensitive, its circuit description is very simple, consisting of 3 CCCCTAs and 2 operational amplifiers, and the proposed circuit is very appropriate for further developing into integrated circuit architecture. The PSpice simulation results are shown. The given results agree well with the theoretical anticipation.

Abstract:
Five new electronically-controllable second order current-mode sinusoidal oscillators using three mul-ti-output operational transconductance amplifiers (MO-OTAs) and two grounded capacitors (GC) have been presented. Simulation results are included to confirm the theoretical analysis based upon CMOS OTAs implementable in 0.5 µm technology.