Ravindra K. Sharma

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.

Universal current mode biquad using a single CFOA

Because of their several advantages over the traditional voltage mode op-amp, current feedback op-amps (CFOAs) have attracted prominent attention as alternative building blocks for biquad filter realization. Previously known universal current mode (CM) biquads (i.e. those capable of realizing all five generic filter functions, namely low-pass, band-pass, high-pass, notch and all-pass) are realizable with CFOAs but require two to nine CFOAs. Although a few dual-function/three-function single-CFOA-based CM circuits have appeared in the literature, no single-CFOA-based canonic universal CM biquad with explicit CM output has been reported until now. This paper presents such a circuit. The workability of the proposed circuit has been confirmed by PSPICE simulations based upon AD844-type CFOAs.

Explicit-current-output sinusoidal oscillators employing only a single current-feedback op-amp

Although a number of sinusoidal oscillators have been described in earlier literature which employ only a single current feedback op-amp (CFOA) to generate voltage-mode sinusoidal oscillations, any sinusoidal oscillator circuit, which can provide a current-mode output signal explicitly (i.e. from a high output impedance node) while using only a single CFOA, has not been reported till date. This letter describes two such circuits and demonstrates their practicability through experimental results based upon AD844 type IC CFOAs.

Multifunction CM/VM Biquads Realized with a Single CFOA and Grounded Capacitors

Abstract New configurations are proposed which realise multiple-input-single-output-type multifunction current mode and voltage mode biquads capable of realizing the low-pass, band-pass, high-pass, and notch functions from the same configuration using only a single current feedback op-amp, four resistors and two grounded capacitors. The new circuits offer several advantageous features over the previously known single-current feedback op-amp/second generation current conveyor-based biquads. Electronic tunability of ω o is feasible by replacing the resistors by appropriately-valued CMOS voltage-controlled-resistors driven by a common external control voltage. PSPICE simulation and hardware implementation results are given which have demonstrated the workability of the proposed configurations.

A NEW ELECTRONICALLY-TUNABLE ACTIVE-ONLY UNIVERSAL BIQUAD

A number of configurations for realizing voltage-mode (VM) biquads using op-amps and OTAs have been presented in the literature, however, none of these provide the following desirable properties simultaneously: (i) realizability of all the five standard filters (namely; low pass, high pass, band pass, band stop and all pass), (ii) tunability of all the three filter parameters (namely; ω0, bandwidth or Q0 and gain) and (iii) not requiring any realization condition in any of the five filter responses. This paper presents a new configuration which does possess all the above mentioned desirable properties simultaneously while using only two internally-compensated type op-amps and a reasonable number of OTAs. The workability of the new configuration has been demonstrated by SPICE simulations based upon CMOS Op-amp and CMOS OTAs.

Electronically-controllable floating inductor using OMA with enhanced input dynamic range

Recently a new formulation for realizing a floating inductance (FI) using an OMA (operational mirrored amplifier), which takes into account the dominant pole of the op-amp employed in the OMA, without requiring any external capacitor was proposed. The proposition, however, suffered from a limited input-dynamic-range of operation owing to limited open-loop signal handling capability of the op-amp used. In this paper we propose an improved FI formulation with increased input signal handling capability. The electronically controllable floating inductance feature of the resulting circuit has been shown by replacing all the building blocks of the FI formulation by their CMOS counterparts. The workability of the proposed FI has been demonstrated by PSPICE simulations.

ELECTRONICALLY-CONTROLLABLE FLOATING INDUCTOR USING OPERATIONAL MIRRORED AMPLIFIER

The operational mirrored amplifiers (OMA) were introduced as useful building blocks for facilitating an easy realization of floating impedances (in conjunction with RC elements) as compared to other approaches of floating impedance simulation. In this paper, we present a new formulation, for realizing a floating inductance (FI) using an OMA which takes into account the dominant pole of the op-amp employed in the OMA and hence, does not require any external capacitor. Moreover, when the only external resistor employed is replaced by an electronically-controlled resistance, the resulting circuit permits an electronically controllable floating inductance. The workability of the proposed FI has been demonstrated by PSPICE simulations.