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This paper presents a new feedback model that focuses on the synthesis rather than the analysis of feedback amplifiers. First, a single-loop synthesis-oriented feedback model is developed that enables the full synthesis of such amplifiers in a hierarchical and systematic way. This model is subsequently extended to a double-loop synthesis model, so that also feedback amplifiers with a characteristic input or output impedance-employing two feedback loops-can be synthesized through the same systematic approach. That these new models are suitable for synthesis lies in the fact that they map directly to the circuit level, such that the intended, asymptotic behavior as well as the various individual contributors to the deviation from this intended behavior, like finite loop gain, non-ideal input and output impedances of the forward gain block, direct feed-through and attenuations outside the feedback loop(s), are clearly distinguished and can be assigned to the responsible sections of the network. For this purpose, the double-loop synthesis model makes the transfers of the two feedback networks explicitly visible, so that it gives immediate insight in how to design these networks to get the required signal transfer and characteristic impedance. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper two filter configurations one operating in voltage-mode (VM) and the other in trans-impedance-mode(TIM) with each employing three non-inverting current feedback amplifiers (CFAs) along with seven passive components are presented. The VM filter with three inputs and three outputs enjoy the features of: realizing all the generic filtering functions by proper choice of inputs with three responses simultaneously, ideal for cascading due to its inputs at high impedances and outputs at low impedances, and realizing trans-admittance-mode(TAM) filtering functions from the same topology. The TIM circuit with a single input and three outputs has the features of: realizing three filtering functions simultaneously, ideal for cascadibility because of having input at zero impedance and outputs at low impedances, and implementing current-mode(CM) filtering responses from the same configuration. These filtering topologies besides having low active and passive sensitivities show that their filtering parameters cut-off frequency (ω0), bandwidth(ω0/Q), quality factor(Q) and gain(H0) permit either orthogonal or independent adjustment .The current and voltage tracking errors of the active devices have been included and to confirm the theoretical analysis, experimental and PSPICE simulation results are shown. [ABSTRACT FROM AUTHOR]

The Blackman's impedance relation formula holds several unique and important features. First and most important is generality. The formula is truly universal and could be applied regardless of feedback topology. The impedances of canonical cases could be presented as special cases of Blackman's impedance relation. This paper revisits the concepts of Blackman's impedance relation. Several alternative derivation approaches are suggested to stand in accord with the gain evaluation procedure. The derivation of the Blackman's impedance relation formula by Superposition, Thevenin, Trans-Admittance and Trans-Impedance methods are offered. The paper extends the ideas and completes the methodology of unified approach to analysis of feedback amplifiers presented earlier. The paper also discusses some additional features of the feedback amplifier model. The paper advocates that the described method of obtaining the loop-gain makes a real difference in application of the formula. Overcoming the loop-gain computational difficulties helps reestablish the Blackman's impedance relation as a viable tool in analysis of feedback circuits. [ABSTRACT FROM AUTHOR]

This paper suggests a pedagogical approach to teaching the subject of the analysis of feedback amplifiers for electrical engineering students at the undergraduate level. Special attention is given to derivation of the input and output impedances. In order to make the procedure clear and suitable for classroom presentation an alternative proof of the Blackman's Impedance Relation is derived to stand in accord with feedback amplifier analysis methodology presented earlier. The proposed analysis technique is algorithmic, comprehensive, suited to any feedback topology, and is especially useful in cases that do not readily stand out as one of four canonical cases of feedback. The methodology is demonstrated by examples, and supported by comparison with simulation and other theoretical results. [ABSTRACT FROM AUTHOR]

The stacked-device power-combining technique is a proven method to increase the output power and load impedance of a power amplifier (PA) simultaneously. The series-input configuration is physically realizable for multicell stacked device configuration in monolithic circuits. The series-input and series-output stack configuration is rigorously analyzed and proven to increase both the input impedance and output impedance simultaneously, easing the matching circuit designs in high PAs. The effects of asymmetry of the input feed and amplifier cells due to distributed effects and process variation on the performance of the stack amplifier are discussed. A four-cell HBT amplifier operating at 5-6 GHz is demonstrated to validate the circuit concept. [ABSTRACT FROM AUTHOR]

A new high input impedance filter employing three current feedback amplifiers (CFAs) and six passive elements, three of them are grounded, is presented. The proposed circuit offers the following advantages: simultaneous realization of lowpass (LP), bandpass (BP) and highpass (HP) filtering functions, employs two grounded capacitors, exhibits high input and low output impedances which permits easy cascade connection, low passive sensitivity figures and orthogonal control of resonance frequency (ωo) and bandwidth (ωo/Q). PSPICE simulation results are given to verify the theoretical calculations. [ABSTRACT FROM AUTHOR]

Negative impedance converter circuits (NICs) are important building blocks in design and manufacturing of analog and mixed mode integrated circuits. In this paper, a catalogue of single-current feedback amplifier-based negative impedance converter circuits having impedance scaling properties is proposed. Various examples are presented to illustrate the versatility of the proposed NIC circuits. [ABSTRACT FROM AUTHOR]

A new configuration for realizing a higher-order series impedance function using current-feedback amplifiers (CFAs) is presented. The nth-order series impedance function employs only (n-1) CFAs and (2n-1) passive elements. The higher order series impedance function can be applied to realize various higher-order highpass and lowpass filters. The passive element values can be easily decided from the coefficients of the filter transfer functions. The use of CFAs simplifies the circuit implementation and makes the proposed circuit attractive for application. Experiments and simulation results are given to confirm the theoretical analysis. [ABSTRACT FROM AUTHOR]

Examines the bandwidth behavior of negative-feedback amplifiers with dominant pole compensation. Analysis of general feedback amplifier topologies; Influences affecting transimpedance configuration bandwidth; Capabilities of a transconductance voltage amplifier.

We report the development of a wide-bandwidth, low-noise front end to facilitate the high frequency operation of both LTS and HTS DC SQUIDs. A transformer of novel design non-resonantly matches the dynamic impedance of the SQUID through a twisted pair to a room-temperature amplifier. The amplifier uses active feedback techniques to flatten the response of the signal path. When operated in conjunction with the high frequency SQUID feedback electronics (developed by IBM T.J. Watson Labs) with a modulation frequency of 16 MHz, and a Quantum Design DC SQUID, the system achieved a slew rate of 1.9/spl times/10/sup 6/ /spl Phi//sub 0/ s/sup -1/, a closed-loop performance of 5 MHz and a noise level of 5.5 /spl mu//spl Phi//sub 0//(Hz)/sup 1/2/. The response from SQUID input to amplifier output was relatively flat from 2 MHz to 25 MHz, with usable signal to 45 MHz. We believe the performance is limited by cabling and expect significant improvements in miniaturized design. [ABSTRACT FROM PUBLISHER]

Uncoupling of feedback-amplifiers results in amplifiers of which the input and output impedance has the same value as from the feedback-amplifier, but with the internal current source depending on the manner of feedback connection, thus complete unilateralization. The same holds for double feedback-amplifiers, such as a gyrator.
It is well-known that the amplification of a feedback-amplifier can be expressed by A = A(1 - A), (1) where A is the amplification of the non-feedback-amplifier and the feedback factor. It is also known how the input and output impedance of the amplifier is changed, due to the feedback, depending on the manner of feedback connection (Alexander 1968).
In the following we will use the formula for these impedances to construct the scheme of an amplifier without feedback, which has the same amplification and input and output impedance as the feedback-amplifier. [ABSTRACT FROM AUTHOR]

This letter comments on the recently published paper in [] which provides realizations of minimum component quadrature sinusoidal oscillators. On re-examination of the 'Type 3' oscillator circuits in [], it has been found that the circuits actually suffer from 'latch up' problem due to use of incorrect polarity of the CCII based negative-impedance convertor. This problem has been corrected (without altering the characteristic equation) by swapping the impedances at y and x terminals. Explicit quadrature current outputs are derived similarly as done in []. [ABSTRACT FROM AUTHOR]