Raj Senani

Realization of a class of analog signal processing / signal generation circuits : Novel configurations using current feedback op-amps

In this paper, we demonstrate that, when treated as 4-terminal building blocks, the current feedback op-amps (CFOA) or transimpedance op-amps are more versatile than the traditional 3-terminal op-amps and 3-terminal Current Conveyors (CC), In realising a class of analog signal processing / signal generation functions which include impedance converters / inverters, voltage-controlled impedances (both grounded and floating), active filters (both current mode and voltage mode) and single-resistance-controlled/voltage-controlled sinusoidal oscillators. Novel CFOA-based configurations are, therefore, derivable which provide features all of which are not possible with the available op-amp-based or CC-based reallsations. The workability of the new structures is substantiated by experimental results based upon the commercially available transimpedance op-amp AD844.

New current-mode biquad filter

A new current conveyor-(CC-)based active biquadratic filter configuration is proposed. The proposed structure offers the following advantageous features in contrast to the previously known CC-based current mode filters: (i) the realization of all the five generic filter functions (namely, low-pass, band-pass, high-pass, notch and all-pass) from the same configuration without requiring critical matching conditions/cancellation constraints; (ii) use of only two grounded capacitors; (iii) availability of non-interacting tunability of the parameters of the realized filters through grounded resistors; (iv) employment of all grounded RC elements; (v) easy conversion into a voltage mode biquad; and (vi) suitability for IC implementation. The workability of the proposed structure has been demonstrated by the results of SPICE simulations based upon translinear CC implementations.

A novel application of four-terminal floating nullors

It is shown that four-terminal floating nullors provide a novel solution to the problem of RC-active synthesis of floating immittances.

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

Novel single-resistance-controlled-oscillator configuration using current feedback amplifiers

A novel configuration is presented which can realize single-resistance controlled active-RC and active-R oscillators and low-pass/band-pass filters from the same structure.

Bibliography on Nullors and Their Applications in Circuit Analysis, Synthesis and Design

A bibliography on research work related to ‘nullors’ and their applications in circuit analysis, synthesis and design, covering the period 1961–2000, is given.

A simple approach of deriving single-input-multiple-output current-mode biquad filters

The classical passive LCR filter structures have been used in the past in deriving low-sensitivity voltage-mode active-RC, active-R, switched-capacitor, Current-Conveyor (CC)-based, OTA-C, MOSFET-C and digital filters, in a variety of ways. In this paper, we present an extremely simple, yet previously unreported, way of using a passive LCR prototype to derive biquadratic current mode active filters. It is shown that the proposed method, though simple, indeed has the potential of producing interesting current mode biquads as exemplified by the new CC-based CM biquad structures derived here.

On equivalent forms of single op-amp sinusoidal RC oscillators

It has been known that a given single op-amp RC sinusoidal oscillator has four distinctly different, equivalent, stable forms, This paper shows that with the op-amp replaced by a four terminal floating nullor, the number of such equivalent realizations of any given single op-amp oscillator are much more than four. Through some examples it is demonstrated that some of such additional realizations of a given op-amp oscillator, are likely to have some interesting properties not available in the usually derived four equivalent forms of the same oscillator, The theory is supplemented with examples and verified by SPICE simulations and experimental results. >

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.

On the realization of floating active elements

Recently, it has been shown by Paul-Dey-Patranabis that a floating NIC can be realized with two second generation current conveyors (CC), without constraints. In this communication it is shown that more useful floating generalized positive immittance converter/inverter elements too can be realized with only two second generation current conveyors.