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There are many active RC networks that implement the low-pass filter characteristic. It has been the common practice to compare these networks with regard to passive element sensitivities while assuming the amplifier to be ideal. Such an assumption gives results that disagree with experimental observations, particularly when the pole magnitudes are large. This paper characterizes the amplifier by a one-pole rolloff model and discusses the ensuing limitations on four widely used low-pass realizations. The amplifier's open-loop gain-bandwidth product is used as a parameter to generate complex-pole loci that graphically display the effect of the nonideal amplifier. The expression of the slope of these curves at the nominal pole positions is derived and first-order estimates for the resulting changes in the \omega_{0} and Q of the poles are given. These expressions can be used to determine the upper bound on the frequency \omega_{0} that these networks can effectively realize. Experimental results agree with the predicted changes. The methods have also been applied to high-pass, bandpass, band-reject, and other realizations.

An amplifier module using a novel surface-wave bandpass filter for a spread spectrum communication receiver has been designed to realize wide-band low-shape-factor requirements. This module with a center frequency of 168 MHz has a midband gain of 6 dB, a 7.1 percent fractional bandwidth (3-dB bandwidth of 12 MHz), and an extremely low-shape factor of 1.32 to 1 (ratio of 3 to 40-dB bandwidth). Excellent agreement is cited between the theoretical frequency and impulse responses of the surface-wave bandpass filter and its measured performance.

This paper gives an account of the studies carried out on a filter type of up-converter Parametric Diode Amplifier operating on the sum-mode at a signal frequency of 755 Mc/s. and pump frequency of 9805 Mc/s. The diode used was a Kita diode type GSB-1A with a cut-off frequency of 60 kMc/s. At the output of the amplifier, a bandpass filter has been provided to select the signal at the output frequency and a band rejection filter to eliminate the pump frequency. The paper gives a brief account of the amplifier designed and also of the measurements carried out.

Frequency active filters are designed by treating the operational amplifier as ideal. Consequently, the actual circuit's performance may depart considerably from what is expected. This is demonstrated in the design of an active bandpass circuit. However, it is shown that good agreement results between the predicted and actual performance if the operational amplifier's frequency dependence and output resistance are taken into account. Expressions are derived for the pole shift caused by the nonideal amplifier. Subject to given constraints, quantitative results are given that establish an upper bound on the frequency of operation of the bandpass circuit.

A new bandpass filter using the operational-amplifier pole and a single external capacitor has been described. It has been shown that the circuit can realize infinite pole-frequency Q product. The applicability of the circuit for realizing bandpass filters and oscillators has been investigated.

The utilization of the operational amplifier pole in the design leads to filters with satisfactory high-frequency performance. The approach reduces the number of capacitors required leading to circuits suitable for integration. Circuit arrangements for a bandpass filter and a second-order Butterworth low-pass filter have been suggested using only resistors and two operational amplifiers. The circuits have low parameter sensitivities.

Generalization schemes and illustrative examples are given for a class of high- Q high-frequency two amplifier active RC networks using all-pass circuits with either positive or negative gain constant. In this preliminary study, the \omega_0 and Q degradations of the networks are compared with the state-variable filter. Experimental results for a bandpass filter application are included.

A general configuration for realizing a high Q notch filter is given. The circuit has a very high input impedance and a very low output impedance. The frequency limitation equations based on the one-pole roll-off model of the operational amplifier are given.

A new bandpass filter with low pole frequency (ωp) and high selectivity (Q) derived from state variable technique is described. Design equations and sensitivity figures are also presented.

Inverting integrators are dependent upon the open-loop frequency response of the amplifier. Improvement in frequency performance of an order of magnitude is achieved with two-pole versus single-pole compensation for the same amplifier. Amplifier output impedance can affect integrator frequency response.

A novel realization of an SC wave bandpass filter is presented. A tenth-order bandpass filter is given as an example. Only six operational amplifiers are needed for the realization, which is parasitic-insensitive.

Three recently proposed grounded capacitor active filters using the amplifier pole have been compared. Some limitations of these circuits for realizing bandpass filters at low frequencies, due to the finite ω a of the operational amplifier, are discussed. These circuits are also compared with other input-capacitor based bandpass filters.

A simple bandpass amplifier is presented which exhibits a very high gain, selectivity, and input impedance. The amplifier has a very narrow bandwidth and a high Q factor.

The importance of Q sensitivity is shown. Several networks are compared. In many cases adequate stability can be achieved with a single operational amplifier per complex-pole pair.

Noninverting operational amplifiers cannot readily be used for various Sallen and Key filters because they cannot provide gain less than unity. A simple network modification is suggested that overcomes this limitation and introduces an added degree of freedom with parameters that are determined by passive components only.

The sensitivity, to μ−1 (where μ is the open-loop amplifier gain), of the Q factor of a 2nd-order Sallen-Key circuit can be reduced from the conventional value 2Q2/μ to 3Q/μ by increasing the closed-loop gain from 1 to 4/3. However, this increases the sensitivity to passive-element variations. An optimum engineering solution is found by minimising, for given maximum component variations, the resulting variation of Q, rather than the sensitivities. This makes single-amplifier circuits usable for higher Q factors than previously, which is of particular interest for microelectronic realisations of such circuits.

In the active distributed RC low-pass filter circuit studied by Wyndrum, a non-zero output impedance of the amplifier results in a rejection filter characteristic, instead of a low-pass characteristic. A simple method of avoiding this undesirable effect is reported in this note.

A second-order bandpass filter using one of Antoniou's gyrator is discussed, which is found to be little affected by the nonidealities and the nonlinearity of the operational amplifiers, and seems to be ideally suited for high-Q and high-frequency applications. A model to study the effects of slew-rate on the filter is proposed, which can be applied to any circuit configuration, involving any number of operational amplifiers. Copyright ? 1981 by The Institute of Electrical and Electronics Engineers, Inc.

The paper describes a simple high-Q insensitive active band-pass filter having relatively few passive components and active elements with low closed-loop gains, using positive feedback Q enhancement scheme. The proposed filter has minimum dependence on the bandwidth of the operational amplifiers and is capable of operating over a wide frequency range with relatively stable Q and resonant frequency.

A bandpass filter using only two registors and two operational amplifiers is suggested. The circuit has a Q equal to the ratio of the resistors. While Q and gain are insensitive to temperature variations, the variations in center frequency is minimized using a compensation scheme. Copyright ? 1974 by The Institute of Electrical and Electronics Engineers, Inc.

Multiple coupled high Q cavities can be used to generate even order elliptic function bandpass filter responses. This paper describes the design of odd order elliptic function bandpass filters using a minimum number of cavities connected by simple and resonant coupling elements. Experimental results of a 3-pole, 20-MHz bandpass waveguide cavity filter centered at 3890 MHz correlate well with theory.

A double-integrator active-RC filter is described, in which both Q and frequency sensitivity to the operational-amplifier Gain-bandwidth product are made zero by active-compensation techniques. The circuit can be used for high-Q high-frequency applications. Copyright ? 1977 by The Institute of Electrical and Electronics Engineers, Inc.

The pole of an operational amplifier and a grounded capacitor are used for obtaining a high Q bandpass function. The utilization of the pole of the operational amplifier enables the extension of its useful frequency range. The gain and the bandwidth of the operational amplifier are the primary factors determining the filter performance. The experimental results of a low-sensitivity filter circuit are presented. The circuit is suitable for integration. Copyright 1973 by The Institute of Electrical and Electronics Engineers, Inc.

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This paper presents a new inverter output filter topology for pulse width modulation (PWM) motor drives. It is shown that the proposed filter effectively reduces high frequency harmonics which can cause serious damage to the motor bearings and insulation. The proposed filter is comprised of a conventional resistance, inductance, capacitance (RLC) network cascaded with an LC trap filter. The LC trap, tuned to the inverter switching frequency, is very effective in reducing the switching harmonics. By using this new topology the need for high damping resistance and low RLC cut-off frequency is eliminated. This reduces the phase shift in the current regulation loop and increases the filter efficiency. Experimental verification of the filter topology is provided with a 180 V inverter and a 25 hp permanent magnet synchronous motor. Space-vector predictive current regulation is implemented as an inner-loop current regulator for the outer-loop speed control using a digital signal processor. The effectiveness of the filter at different motor speeds is presented.

In this paper, a high Q tunable 2nd order band-pass filter, working in the RF frequency range and designed in a standard AMS 0.35/spl mu/m CMOS technology, is proposed. The filter is based on three different stages that perform the input and output impedance matching, the bandpass function and prevent instabilities; therefore, it is suitable for integrated front-end RF applications. Simulation results have shown a tunable range between 500 MHz and 1.3 GHz with good input and output impedance matching and a low noise figure. Moreover, this circuit presents a compression-point level higher than -22dBm and a quality factor Q higher than 60.

Using the single-pole model of the operational amplifier (OA) a grounded capacitor network has been analyzed to yield either a bandpass or a low-pass function by adjustment of a single resistor. The bandpass/low-pass filters are suitable for high selectivity applications at extended frequency ranges with the advantage of independent adjustment of pole-frequency, pole-Q factor, and midband/passband transmission gain. The network has low sensitivity to all the circuit parameters. The experimental results are quite in agreement with the analysis.

A new configuration for activating a passive-RC bandpass building block to realize an inverting selective bandpass filter is described. The proposed network has the advantages of being canonic, is always stable, and has reduced sensitivity to the amplifier gain-bandwidth product.

The operational amplifier rolloff characteristics and a single capacitor are used for obtaining an inverting bandpass function. The filter performance depends on the gain-bandwidth product of the operational amplifier. Experimental results are included. The amplifier rolloff characteristics can be utilised in deriving transfer functions. The resulting filters have an extended frequency range of operation and a reduced number of external capacitors.

The design of a stable active RC bandpass filter for general-purpose laboratory use is presented. Noninteracting controls are provided for frequency Q and peak gain.

An arbitrary open-circuit voltage transfer function whose poles and zeros may be independently controlled is realized using RC elements and at most (2n + 2) operational amplifiers, with adjustable gains, where n is the higher of the degrees of the numerator and denominator polynomials of the transfer function.

A distributed RC notch filter with an improved frequency selectivity is described. An extremely insensitive bandpass amplifier can be obtained by use of such a filter.

An active RC filter employing a voltage amplifier as the active element has been chosen. The root sensitivity of the filter with respect to change in the gain of the amplifier has been calculated and minimized to establish a method of synthesis for achieving stability of center frequency and bandwidth.

Refers to an article by G. S. Moschytz (see abstr. B6114 of 1968) that gives consideration to the realization of a second-order transfer function of specified form through utilization of RC elements plus a noninverting operational amplifier. Moschytz claims in the abstract that he has presented a suitable realization, a modified Sallen and Key network, that contains a noninverting amplifier having a gain that can always be made greater than or equal to unity. Such a gain then permits one to incorporate a noninverting operational amplifier into the design. This correspondence shows that there exists a subclass of second-order transfer functions that, when realized by Moschytz's realization procedure, results in a gain constant that is less than unity for all values of the available parameters. It is then not possible to incorporate a noninverting operational amplifier without altering the network structure. A simple modification of Moschytz's work is presented that assures the existence of a realization that includes a noninverting operational amplifier.

Horowitz's active RC synthesis procedure with a voltage controlled current source is combined with Sheingold's realization of the active element using a differential-input operational amplifier to derive a circuit for an all-pass filter of any arbitrary order, having poles confined to the negative real axis only. Illustrative examples are worked out for the first- and second-order cases.

This letter contains a generalization of some recently published RC active all-pass networks using a differential-input operational amplifier and presents a synthesis procedure for all-pass transfer functions of any arbitrary order, having poles confined to the negative real axis. Examples are given to illustrate the synthesis procedure.

The single-pole rolloff of the operational amplifier is used to realise 2nd-order bandpass filters with one external capacitor. These filters have low sensitivity to all the circuit parameters and are suitable for high-frequency medium-Qfactor operation.

A synthesis procedure for generating second-order active filters using the operational amplifier pole and a single external capacitor is given. The proposed method is based on drawing the signal-flow graph from the given transfer function and obtaining the circuit realization from the graph.

A systematic-realisation technique of the 2nd-order active-R filter using an inherent amplifier pole is proposed. To realise such a filter it is shown that two operational amplifiers and three resistors are sufficient. Workede examples are given. The resultant filters are found to be suitable for high-frequency low-Q-factor applications.

The exact mathematical solution of the amplifier finite gain and bandwidth problem in switched-capacitor filter networks is presented. The theory is incorporated into a computer analysis program and typical results for a filter circuit are included.

A configuration for realising a 2nd-order bandpass filter based on the single-pole roll-off characteristics of the operational amplifier with a single grounded external capacitor is presented. The filter has low sensitivity to all the circuit parameters. Experimental results verify its suitability in high-frequency applications with moderately high selectivity. Independent control of centre frequency, frequency selectivity and midband gain is possible.