D. R. Bhaskar

New current-mode universal biquad filter

A new current-mode universal biquadratic filter using only two second generation current conveyors and a minimum number of passive components is presented. The proposed configuration can realize the second-order low pass, high pass, band pass and band reject responses simultaneously. The validity of the proposed formulation is confirmed by PSpice simulation results.

New CFOA-Based Single-Element-Controlled Sinusoidal Oscillators

New single-element-controlled sinusoidal oscillator (SECO) circuits using only two current-feedback operational amplifiers (CFOAs) and only five passive elements [two/three grounded capacitors (GC) and three/two resistors] are presented, which not only enlarge the previously known class of two-CFOA-GC SECOs but also provide new configurations that possess properties not available in the previously known circuits. The new oscillators are useful from the viewpoint of applications in several instrumentation and measurement situations such as oscillator-based capacitance measurement schemes, realization of very low frequency oscillators, and the design of voltage-controlled oscillators. Experimental results based upon commercially available AD844-type CFOAs are included, which confirm the practical workability of the new oscillator configurations

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.

A simple configuration for realizing voltage-controlled impedances

A simple configuration is proposed that incorporates an effective cancellation of the nonlinearity of the V/sub DS/-i/sub D/ characteristics of the FET to produce a voltage-controlled resistance (VCR) with linear range considerably more extended than other conventional FET-based VCRs. The configuration is shown to be simpler than op-amp-JFET based VCRs yet is more versatile than the previously known circuits. It makes possible the realization of VCC and VCL elements from the same configuration, which cannot be realized from the earlier circuits. CMOS versions of the proposed schemes of the VCC and VCL are suggested. >

Single op-amp sinusoidal oscillators suitable for generation of very low frequencies

The authors present some op-amp-based single-element controlled sinusoidal oscillator structures which can generate very low frequencies (VLF). In contrast to earlier VLF oscillators which have large frequency of the oscillations sensitivities and/or require two to five op-amps, the proposed circuits make it possible to generate VLF oscillations in a minimally sensitive manner while requiring only a single op-amp. The experimental results prove the validity of the theoretical formulations. >

Electronically Controllable Explicit Current Output Sinusoidal Oscillator Employing Single VDTA

A new current-mode sinusoidal oscillator employing a single voltage differencing transconductance amplifier (VDTA), two grounded capacitors, and one grounded resistor has been proposed. The proposed sinusoidal oscillator offers the following advantageous features: (i) use of grounded capacitors which are attractive from the view point of IC implementation as well as eliminating/accommodating parasitic capacitances, (ii) independent control of frequency of oscillation and condition of oscillation, (iii) ready availability of explicit current-mode output, (iv) low active and passive sensitivities, and (v) a very good frequency stability. The workability of the proposed configuration has been established by PSPICE simulations.

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).

Realization of New Electronically Controllable Grounded and Floating Simulated Inductance CircuitsUsing Voltage Differencing Differential Input Buffered Amplifiers

A new active circuit is proposed for the realisation of lossless grounded and floating inductance employing Voltage Differencing Differential Input Buffered Amplifiers (VD-DIBAs). The proposed grounded simulated inductance circuit employs two VD-DIBAs and a single-grounded capacitor whereas the floating simulated inductance circuit employs three VD-DIBAs and a grounded capacitor. The circuit for grounded inductance does not require any realization conditions whereas in case of floating inductance, only equality of two transconductances is needed. Some sample results demonstrating the applications of the new simulated inductors using VD-DIBAs have been given to confirm the workability of the new circuits.