Abdhesh K. Singh

New OTA-C universal current-mode/trans-admittance biquads

This letter introduces two new OTA-C universal Current mode biquads which offer almost all of the desirable features (expected from a good universal biquad) simultaneously, without any trade-offs. With first OTA removed and the input current source replaced by an input voltage source, both the new circuits can also realise trans-admittance-type universal biquad filters. The workability of the new circuits has been established by SPICE simulation results of their CMOS-implementable versions.

Two new canonic single-CFOA oscillators with single resistor controls

Although a number of single current feedback op-amps (CFOA)-based single-resistance-controlled oscillators (SRCO) have appeared in earlier literature, only six of them are canonic (i.e., requiring only two capacitors and only three resistors). The object of this brief is to add to this list two new canonic single-CFOA-based SRCO configurations. An evaluation of these two new circuits has been carried out and their workability of has been confirmed by experimental results based upon AD844 CFOAs.

Active-R design using CFOA-poles: new resonators, filters, and oscillators

Recently, the active-R circuits utilizing the current feedback op-amps (CFOA)-pole have been shown to be superior alternatives to the active-R circuits designed using the compensation-poles of the traditional voltage-mode op-amps. The object of this brief, is to present some new CFOA-pole-based active-R circuits which employ a very small number of active and passive components, and yet, offer features which have not been attained simultaneously from any of the previously known active-R circuits using CFOA-poles such as, noninteracting controls of parameters, and the availability of the intended properties, in spite of the presence and consideration of all the parasitics (even other than those forming CFOA-pole). The workability of the proposed circuits has been confirmed by PSPICE simulations and hardware implementations based on AD844 type CFOAs.

Novel mixed-mode universal biquad configuration

Although a variety of CFOA-based biquads have been known in the literature, any CFOA-based circuit capable of realising universal biquad filters in all the four possible modes i.e. voltage-mode, current-mode, trans-admittance-mode and trans-impedance-mode, has not been reported in the literature so far. In this paper, a novel configuration has been presented, which realises all the five generic filter functions (namely, low-pass, band-pass, high-pass, notch and all-pass) from the same circuit in all the four possible modes, employing only four-Current feedback operational amplifiers (CFOA) along with two grounded-capacitors as desirable for Integrated Circuit implementation. The workability of the circuit has been confirmed by hardware implementation based on AD844 type CFOAs.

OTRA-based Grounded-FDNR and Grounded-Inductance Simulators and Their Applications

New grounded frequency-dependent negative-resistance (FDNR) and grounded inductance simulation circuits, employing an operational trans-resistance amplifier (OTRA) along with two capacitors, two resistors and a voltage follower have been introduced. The application of the new simulators in the realization of a single-resistance controlled oscillator (SRCO) and a single-capacitance controlled oscillator (SCCO) has been demonstrated and the effect of parasitic capacitance and input and output resistances of the OTRA on the performance of these circuits has been evaluated. The workability of the application circuits has been confirmed by experimental results using an OTRA-implemented from commercially available AD844-type current-feedback operational amplifiers (CFOAs).

A NEW FOUR-CC-BASED CONFIGURATION FOR REALIZING A VOLTAGE-MODE BIQUAD FILTER

A new voltage-mode (VM) biquad filter is presented, which employs four Current Conveyors (CC) along with five resistors and only two grounded capacitors, facilitates electronic control of filter parameters through grounded resistors (realizable by FETs/MOSFETs) and is suitable for IC implementation in bipolar or CMOS technology. The circuit offers several advantages over the four-CC-based VM biquads published earlier. The workability of the new circuit has been confirmed by PSPICE simulations.

A new floating current-controlled positive resistance using mixed translinear cells

A simple floating current-controlled positive resistance (CCPR) circuit based upon two mixed translinear cells realized with bipolar junction transistors has been presented. The workability of the circuit and its application in realizing a variable-bandwidth bandpass filter and a new frequency shift keying generator have been confirmed by experiments and/or PSPICE simulations based upon CA3096 and ALA400 mixed transistor arrays. The proposed floating CCPR circuit appears suitable for implementation of a variety of electronically tunable analog signal processing/generation circuits in bipolar technology.

Systematic realisation of quadrature oscillators using current differencing buffered amplifiers

A systematic approach is presented to realise quadrature oscillators using current differencing buffered amplifiers (CDBAs). Based on a general scheme employing a cascade of a special type of low-pass filter and an integrator in a closed loop, a general configuration is formulated that yields 12 single-resistor-controlled-quadrature oscillator circuits using CDBAs an active elements. All the oscillator circuits enjoy fully uncoupled independent control of condition of oscillation and frequency of oscillation using a minimum possible number of active components, grounded/virtually grounded capacitors and grounded/virtually grounded resistors. PSPICE simulation results along with hardware experimental results, based on commercially available AD844 ICs to construct the CDBAs, are included which confirm the practical workability of the new quadrature oscillator configurations.

New Universal Biquads Employing CFOAs

Four new single-input-multi-output-type universal biquad filters using current-feedback operational amplifiers (CFOAs) are presented, which realize all the five standard filter functions (namely, low-pass, bandpass, high-pass, notch, and all-pass) from the same configuration, provide tunability of the various filter parameters in all the five responses, and offer a resistive or ideally infinite input impedance while employing only four CFOAs and two grounded capacitors as preferred for integrated circuit implementation. The workability of the new biquads has been verified by hardware implementations and SPICE simulations based upon AD844-type CFOAs, and some sample results are presented

New canonic lossy inductor using a single CDBA and its application

A new lossy inductor (parallel R-L type) using single current differencing buffered amplifier (CDBA) is presented, which employs only two resistors and a grounded capacitor. The proposed lossy inductor is shown to be useful in realizing an oscillator circuit, which provides quadrature voltage outputs using only two CDBAs, three resistors and two grounded capacitors and offers independent control on condition of oscillation and frequency of oscillation up to a frequency of 61 MHz. Detailed non-ideal analysis including single-pole model for voltage and current gain has also been carried out. SPICE simulation results and experimental results based upon the CDBA constructed from commercially available IC AD844 have been included which confirm the practical workability of the proposed lossy inductor and quadrature oscillator circuit.