Frequency-dependent Negative Resistance Research Articles

High-frequency active filter design using monolithic nullors

A monolithic building block suitable for high-frequency RC active filter implementation is described. The transconductance-type device is fabricated using standard bipolar technology, and its performance is shown to be superior to corresponding voltage operational amplifiers (op amps) at frequencies above 20 kHz. It is also shown that high quality simulated inductance and frequency dependent negative resistance elements can be implemented at higher frequencies than is possible using standard bipolar op amps.

Active simulations using current conveyors

This paper describes some new circuits simulating ideal grounded frequency-dependent negative resistances and ideal floating inductances using second generation current conveyors.

Novel active R supercapacitor simulation: applications in low sensitivity multifunction network realisation

A new configuration containing only two operational amplifiers and a single resistor has been shown to simulate a grounded supercapacitor (D) frequency-dependent negative resistance element based on the usual one-pole rolloff characteristics of the active o.a. device. Appropriate insertion of only one additional RC section yields a novel network with multifilter function capabilities having independent Q and ω0 adjustments at very low active and passive sensitivities. With suitable design, a minimal circuit realisation of a variable frequency active R oscillator can be derived from the proposed configuration.

Realization of frequency dependent negative resistance

A new active network is proposed for realising a frequency dependent negative resistance (FDNR). It employs two second generation current conveyors of the positive type, three resistors and three capacitors. It is further shown that by appropriate choice of components the circuit can realise an RC resonator and a grounded inductance. The sensitivities of the realised elements with circuit components is shown to be low.

A new equal-valued grounded-capacitor resonator realization using current conveyor

Using a second generation current conveyor (CC II), a new resonator network containing a resistance (R)-capacitance (C)-frequency dependent negative resistance (D) series configuration is proposed. The network is canonic and both the equal-valued capacitors are grounded. ω 0 and Q of the resonator have been shown to be practically insensitive to changes in active parameters.

Some observations concerning the methods of filter/oscillator realization using the concept of FDNR

It has been shown that the method of converting a passive RLC low-pass (LP) filter into an inductorless filter using the concept of frequency-dependent negative resistance (FDNR) is equivalent to first applying the low-pass-to-high-pass (LP → HP) transformation and then the RC:CR transformation on the LP filter. Also, the RLC model of an active-RC oscilator and the corresponding RCD model derived from this through Bruton's transformation are RC:CR transforms of each other. The latter observation suggests that many novel oscillator circuits can be generated from existing ones through RC:CR transformation.

Novel active-R ideal frequency-dependent negative-resistance simulation

A novel structure for the simulation of an ideal frequency-dependent negative-resistance (FDNR) element based on the single-pole rolloff characteristics of the operational amplifier is reported. The structure uses only operational amplifiers and a resistor.

Realization of frequency-dependent negative resistance

A simple and elegant method to realize a Frequency-Dependent Negative Resistance (FDNR) with only one operational amplifier is presented. The input arid output admittances of the proposed amplifier configuration realize either a frequency-dependent negatives resistance or a combination of frequency-dependent negative resistance with series-parallel EC configuration. Infinite input impedance is realized by invoking certain constraints on the elements of the network. Input and output admittance/impedance sensitivity analysis is also presented.

On demand realization of a frequency-dependent negative resistance and an infinite input impedance

A simple configuration to realize an ideally infinite input impedance, both negative and positive, using an operational amplifier is presented. It is also shown that the same configuration results in a frequency-dependent, negative resistance at its output terminal.

New ideal active inductance and frequency-dependant negative resistance using d.v.c.c.s./d.v.c.v.s.: applications in sinusoidal-oscillator realisation

A new grounded-capacitor simulation of driving-point impedances of the form as and bs2, corresponding to ideal inductance and frequency-dependent negative resistance (f.d.n.r.) elements, respectively, is presented. The configurations use the minimum of passive components with the d.v.c.c.s./d.v.c.v.s. as the active element. Applications of the active inductance and f.d.n.r. are then proposed in the realisation of some single-resistor-controlled RC oscillators.

Realisation of frequency-dependent negative-resistance circuits using two capacitors and a single current conveyor

Realisation of frequency-dependent negative-resistance circuits using two capacitors and a single current conveyor

Optimum design of active filters using the generalized immittance converter

Design equations are derived for the generalized immittance converter (GIC) when embedded in an arbitrary network. The derivation is based on minimizing the dependence of the GIC transfer function on the op amps' characteristics. Equations for the optimum design of the GIC when simulating inductance and frequency-dependent negative-resistance (FDNR) elements follow as special cases. The optimized GIC's are applied in the design of bandpass filters using Gorski-Popiel's ladder embedding technique. The design procedure is presented in detail and its application is illustrated through the design of a telephone-channel bandpass filter of the twelfth order.

Canonical high-selectivity parallel resonator, using a single operational amplifier, and its applications in filters

The canonical circuit introduced is an active RC circuit using a single operational amplifier, and its input admittance is composed of a frequency-dependent negative resistance (f.d.n.r.) in parallel with a resistor and a capacitor. The quality factor of the proposed circuit can be independently controlled by means of a single grounded resistor. Passive sensitivities and the effects of the nonideal op-amps are given. Applications of the parallel resonator in lowpass and bandpass filters are discussed. Finally, experimental results are presented

On the realization of some low-component frequency generators

Simple circuits of sinusoidal frequency generators are obtained using the frequency-dependent negative resistance (FDNR) approach. The nonideal FDNR's employed in the realizations are canonic, and use a single operational amplifier in low-gain connection. Moreover, they are shown to be easily obtained from the well-known grounded inductance simulators. The oscillators offer active and passive component saving over Genin's circuit.

Canonical high-selectivity parallel resonator, using a single operational amplifier, and its applications in filters

The canonical circuit introduced is an active RC circuit using a single operational amplifier, and its input admittance is composed of a frequency-dependent negative resistance (f.d.n.r.) in parallel with a resistor and a capacitor. The quality factor of the proposed circuit can be independently controlled by means of a single grounded resistor. Passive sensitivities and the effects of the nonideal op-amps are given. Applications of the parallel resonator in lowpass and bandpass filters are discussed. Finally, experimental results are presented

Nonideal performance of single amplifier simulated frequency dependent negative resistances

The effect of the nonideal characteristics of operational amplifiers such as finite frequency dependent gain and output impedance on the performance of some single amplifier simulated frequency dependent negative resistances (FDNR's) is analyzed. Equivalent circuits showing the parasitic elements due to nonideal characteristics of amplifier are given. In two configurations the FDNR is shown to have resistive and inductive parasitic elements in addition to series and shunt capacitances. The experimental results confirm the validity of the equivalent circuits. The effect of the slew rate of the operational amplifier on the maximum signal-handling capability is studied. The analysis and equivalent circuits give a clear physical concept of the effect of the nonideal amplifier characteristics on the simulated FDNR's and can be used for'predistorted design of filters with practical FDNR's.

Design of an Active Filter for Channel Translating Equipment

Design of an active filter to meet the specific engineering requirements for its application in the channel translating equipment has been described. It uses the concept of super capacitor or frequency dependent negative resistor and its active realization by integrated operational amplifiers and RC network. It has been established that this type of active realization gives far superior performance compared to that of conventional LC filter in low frequency range. This technique is particularly useful for designing higher order active filters of lowpass type amplitude/frequency characteristic. The circuit configuration and the component tolerances are suitable for thick/thin film implementation.

On the high-frequency limitations of active ladder networks

High-frequency limitations of a generalized immittance converter (GIC) and leapfrog (coupled-biquad) ladder structures are compared. It is shown that the high-frequency limitations of GIC derived <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> -active ladder filters are improved very significantly by employing simulated-inductance and/or frequency-dependent negative resistance (FDNR) elements for which the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> factor is made virtually independent of the gain-bandwidth products of the two operational amplifiers in each GIC. The behavior of such GIC derived structures with respect to variations in temperature is further improved by using dual operational amplifiers for each GIC instead of individual ones.

Parallel resonator with a resistance and a frequency dependent negative resistance realized with a single operational amplifier

Bandpass <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> active filters can be realized, according to Bruton's transformation method, with resistively coupled parallel resonators which are formed by parallel connecting of a resistance and a frequency-dependent netative resistance. This paper describes a single operational amplifier resonator which has an inherent finite quality factor. Bandpass <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> active filters can be thus implemented when the passband is relatively narrow, with performance characteristics comparable to that of currently used <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</tex> filters, up to frequencies of a few kilohertz.

Exact synthesis of active lowpass frequency-dependent negative-resistance filters

If resistances shunting the terminating capacitors of an active lowpass frequency-dependent negative-resistance (f.d.n.r.) filter are used to provide a d.c. path to the amplifier inputs, a redundant pole-zero pair is introduced. A method is described for designing such a filter so that the pole and zero coincide, and the filter exactly realises the desired transfer function.