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The era of SoC design has great dependency on CMOS circuits owing to its low power and high reliability which could contribute in the effective circuit designing. Here, a unique approach for the designing of voltage tunable current differencing transconductance amplifier (CDTA) is reported for the realization of Kerwin–Huelsman–Newcomb (KHN) filter. The proposed design has been simulated by using Cadence Virtuoso simulation tool with 0.18 $\mu$m technology parameters. This design is based on input voltage-based gain and frequency of operation tuning approach. In this reported design of filter, cutoff frequency can be tailored by input voltage instead of input current. This relaxes the need for the iterative circuit modifications to work in a particular frequency range. Thus, the reported CDTA design is expected to be robust and offers higher design flexibility as there is now no need of iterative designing and calibration in this approach. This also exhibits retained area requirement as per the current state of the art for the KHN filters. Further, the performance of designed CDTA-based KHN filter has also been verified with the existing KHN filters.

The history of Tow–Thomas second-order filter is reviewed. Two alternative generation methods of the Tow–Thomas filter are discussed. The first is a generation method from the second-order passive RLC filter and the second is from the multiple feedbacks inverting low-pass filter using a single op amp. Several forms of the circuit are briefly reviewed. Passive and active compensation methods to improve the circuit performance for high-Q designs are summarized. Spice simulation results are included.

The history of Kerwin–Huelsman–Newcomb (KHN) second-order filter is reviewed. A generation method of the KHN filter from passive RLC filter is presented. Two alternative forms of the KHN circuit using operational amplifier are reviewed. The effect of finite gain-bandwidth of the op amps is considered and expressions of the actual ω₀ and Q are given. Two KHN circuits with inherently stable Q factor are also included. Two new partially compensated inverted KHN circuits are introduced. Active compensation methods to improve the KHN and the inverted KHN circuit performance for high Q designs are summarized. Spice simulation results are given. The progress of the KHN realizations using the current conveyor is also summarized briefly.

A fully cascadable (i.e., low/high input impedance for current/voltage input signals and high/low output impedance for current/voltage output signals) mixed-mode (input and output signals can be voltage or current) universal filter biquad by using three differential difference current conveyors (DDCCs), three grounded resistors, and two grounded capacitors is presented in this paper. The proposed biquad can realize the inverting, non-inverting, and differential types universal filtering responses (lowpass, highpass, bandpass, notch, and allpass) from the voltage and current output terminals without changing the filter topology. The proposed circuit is suitable for cascading in all the four possible modes (i.e., voltage, current, transresistance, and transconductance modes). Moreover, the proposed mixed-mode biquad still enjoys (i) using only grounded passive components, (ii) no need of extra inverting and non-inverting amplifiers for special input signals, and (iii) low active and passive sensitivities. This paper also shows how analytical synthesis can be used to produce the proposed mixed-mode filter circuit. H-Spice simulation results confirm the theory.

A current-mode universal biquadratic filter with three input terminals and one output terminal is presented. The architecture uses two current conveyors (CCs), two grounded capacitors and two grounded resistors; and can realize all standard second-order filter functions — highpass, bandpass, lowpass, notch and allpass. Moreover, the circuit still offers the following advantage features: very low active and passive sensitivities, using of grounded capacitors and resistors which is ideal for integrated circuit implementation, without requirements for critical component matching conditions and very high output impedance. The workability of the proposed circuit has been verified via HSPICE simulations using TSMC 0.18 μm, level 49 MOSFET technology.

To extend the existing knowledge on first-order voltage-mode all-pass filters, this paper presents two novel first-order voltage-mode all-pass sections, each employing single fully differential second-generation current conveyor (FDCCII) being used as the newly obtained fully differential voltage conveyor (FDVC), a resistor and a grounded capacitor. Both the proposed circuits possess high-input and low-output impedance feature, which makes the proposed circuits ideal for voltage-mode systems. Non-ideal study along with simulation results is given for validation.

This paper presents a transadmittance-mode (TAM) universal biquad filter with independently electronic tunability. The proposed biquad filter only employs three operational transconductance amplifiers (OTAs) and two grounded capacitors which are the minimum components count necessary for realizing independently electronic tunability of the parameters ω₀ and ω₀/Q without the need of control factors matching conditions. Moreover, the proposed circuit still achieves nearly all of the main advantages: (i) simultaneous realizations of universal filtering responses (low-pass, high-pass, band-pass, band-reject and all-pass) from the same topology, (ii) versatile input/output functions, (iii) orthogonally electronic tunability of the parameters ω₀ and Q without the need of control factors matching conditions, (iv) no need of any resistors, (v) cascadable feature for all input and output terminals, (vi) no need of extra inverting or non-inverting amplifiers, (vii) the employment of only grounded capacitors, (viii) no component-value constraints (except for allpass filter function) and (ix) low active and passive sensitivity performances. H-spice simulations with TSMC 0.35 μm 2P4M CMOS process technology validate theoretical predictions.

None of the previously reported mixed-mode universal filters can achieve the following important advantage: no need of component matching conditions. This paper presents a new mixed-mode (including voltage, current, transadmittance, and transimpedance modes) universal biquadratic filter with no need of matching conditions (including no need of component matching and no need of input matching conditions). The proposed filter structure with nine outputs employs two plus-type fully differential current conveyors (P-type FDCCIIs), two grounded capacitors, four grounded resistors and one floating/grounded resistor, which can realize voltage, current, transadmittance, and transimpedance modes universal filtering responses (lowpass, highpass, bandpass, notch, and allpass) from the same topology without matching conditions. Moreover, the proposed circuit still offers many important advantages: the employment of two grounded capacitors, the simultaneous realizations of a lot of filtering functions, using only grounded resistors as the control factors of all filter parameters and gains, having controllable gains in current and transimpedance modes without disturbing filter parameters ${\omega }_0$, ${\omega }_0$/Q, and Q, cascadably connecting the former voltage-mode (VM) stage and the latter current-mode (CM) stage, no capacitors bringing extra poles degrading high-frequency performance, and low active and passive sensitivity performances. H-spice simulations with TSMC 0.18$\mu$m 1P6M CMOS process technology validate theoretical predictions.

This paper presents first-order voltage-mode filters using a single current conveyor with an additional X-stage, and passive elements. The new circuits have multifunction capability, and also realize low-shelf, high-shelf and band-shelf functions. The study is carried out on the effects of non-idealities, parasitic elements, and loading on the performance of proposed circuits. Active and passive sensitivities are also analyzed. The active element, extra-X current conveyor used for designing new circuits is simpler than most of the one active element and two passive elements’ based circuits. Detailed comparisons are carried out with relevant available works, and the new circuits are found to be more compact and exhibit higher frequency performances. The simulation results using 0.25$\mu$m CMOS parameters with $\pm$1.25V power-supply are shown to verify the proposed circuits. The proposed circuits are also verified through simulations. Experimental support is given using AD-844 ICs to strengthen the validity of the proposed circuits.

This paper introduces an electronically tunable mixed-mode universal biquad filter configuration employing four single output operational transconductance amplifiers (OTAs), one dual output OTA and two grounded capacitors (GCs) (ideal for integrated circuit implementation and absorbing shunt parasitic capacitances). The presented structure can realize all second-order filter functions, namely, low pass (LP), high pass (HP), band pass (BP), band reject (BR) and all pass (AP) responses in voltage mode (VM), current mode (CM), transresistance mode (TRM) and transconductance mode (TCM) using appropriate selection(s) of input signals. The cut-off frequency ($f_o)$ and bandwidth (BW) of the realized filters can be tuned orthogonally through the transconductance (by varying the bias currents) of the OTAs. The proposed biquad configuration enjoys low active and passive sensitivities. The workability of this multifunctional biquad filter topology has been confirmed through simulations using MATLAB and Analog Design Environment (ADE) spectre tool provided by Cadence Virtuoso, using 0.18$\mu$m CMOS process parameter. The post-layout simulations have also been carried out to validate the theory.

In this paper, the method for the design automation of a narrow band-pass amplifier, and hence the amplifier tuned oscillator is discussed. A fixator approach is utilized in this method to design the narrow band-pass amplifiers and a reference circuit is required for this process. The fixator–norator pair helps to generate an extra sub-circuit, generally the feedback network; the addition of this sub-circuit in the actual amplifier circuit will modify the frequency response of the amplifier. The amplifier now behaves like an active narrow band-pass filter, which exactly follows the frequency response of the model circuit. This can be turned into an oscillator by providing positive feedback. Such a circuit possesses independent frequency and amplitude control. Hence, the re-designed circuit can be employed as an active filter or an oscillator at the selected center frequency. In addition to the technical merits, the proposed method has pedagogical importance. Few case studies are worked out in this paper to demonstrate the method.

This paper presents an independently tunable, four-input, three-output, voltage-mode (VM) biquad filter consisting of four operational transconductance amplifiers (OTAs) and two grounded capacitors. The proposed circuit can simultaneously realize three basic biquad filtering functions for single input and three outputs. All five standard biquad filtering functions can be implemented with four inputs and single output by appropriate application of input voltage signals. The developed biquad filter with high input impedances enables noninteractive control of natural angular frequency and quality factor. By slightly modifying the proposed biquad filter, the VM quadrature sinusoidal oscillator with noninteractive control for the oscillation condition and the oscillation frequency has been achieved. Simulation and experimental results are used to validate theoretical predictions.