Types Of Operational Amplifiers Research Articles

An Example of Performance Achievement Based on Errors Analysis for Low-Cost Circuits Design

To create high-performance equipment, low-performance components, such as those from the old generations, can also be used. For example, if a conditioning stage (amplification/attenuation or filtering) is made with high-end components having increased performance, the costs are appropriate – using “classical” functional ones, the price of the equipment will become competitive. Low-cost devices may have features that do not make them attractive for inclusion in high-performance equipment but certain errors’ analysis may lead to practical and useful results. A converter circuit from PWM pulses to DC voltage was used. Experimental determinations were made using several types of operational amplifiers and errors analysis and correction was carrying out.

THE AGING INFLUENCE MINIMIZATION METHOD FOR OPERATIONAL AMPLIFIERS WITH THIN OXIDE TRANSISTORS

Nowadays CMOS technology feature size is being scaled aggressively. Supply voltage is not proportionally scaled, gate dielectric thickness is reduced and as a result, the devices are subjected to stronger electric fields, thereby causing stress on transistor. Stress causes aging degradation, which can lead to dramatic consequences on mobile devices, aircraft, military systems, or medical devices. A method is proposed for designing two types of operational amplifiers with usage of only thin oxide devices, which are protected from stress conditions, namely from aging degradation. The proposed methods can also be implemented on other types of operational amplifiers.

Electroacoustical evaluation of a prototype headphone amplifier for educational purposes

In several classroom activities, it is required to feed a signal simultaneously to several headsets to have students listening to the same sound signal, e.g., to show binaural effects. To drive several headphones, an appropriate headphone amplifier is needed. The aim of this work was to build a prototype of a simple headphone amplifier based on a publicly available project around different types of operational amplifiers and test its electrical and acoustical performance when used with typical headphones. Frequency response function, total harmonic distortion, and signal-to-noise ratio were evaluated. Among the different OPAMPs the OPA2134 showed the best performance, especially because of the very flat frequency response function in the hearing range, low harmonic distortion, and superior SNR (−83 dBFS). Acoustical test were therefore performed based on the amplifier with the OPA2134 only, using a Sennheiser HD 600 headphone and a Sennheiser KR4 microphone. THD measured with this configuration ranged from −86 [email protected] kHz and global SPL = 70 dB to −35 [email protected] Hz and global SPL = 110 dB. At all, the test showed that the amplifier circuit is appropriate for the required application, taking into account that it is very simple and can be mounted easily by the students.

Analog and Logic High Temperature Integrated Circuits based on SiC JFETs

Harsh environment applications such as electrical actuation on military and commercial aircraft, advanced engine controls, downhole energy exploration, propulsion systems of hybrid and all electric vehicles, and space exploration require sensor interfaces, control circuits, and power systems with electronics capable of operating at high temperatures. Wide band-gap materials such as SiC can be used to build devices with high operating temperatures due to their fundamental material properties. This paper presents initial results on developing basic analog and logic integrated circuits based on SiC JFET technology. Analog and logic integrated circuits were built using enhancement vertical channel lateral JFET transistors, metal film resistors and lateral p-n diodes. The analog circuits built include different types of operational amplifiers. The logic circuits include NOT, NAND, AND, NOR and OR gates. Transistors and integrated circuits were packaged in ceramic DIP packages and tested at temperatures up to 500 °C. The tested JFETs show proper operation up to the maximum tested temperature of 500 °C. The operational amplifiers remained functional at temperatures up to 430 °C. Basic logic circuits showed proper operation up to the maximum tested temperature of 500 °C.

An alternative method to quantify the electromagnetic immunity based on the Weibull distribution

It is accepted that the electromagnetic interference should be addressed with statistical analysis. Usually the impact of electromagnetic interference on different electronic samples is evaluated and the average immunity level is used as a reference. However, this method does not provide enough information to know the probability of failure to the electromagnetic interferences of an electronic circuit. An alternative statistical analysis based on the Weibull distribution is presented. The typical and proposed methods have been compared in order to analyse the electromagnetic immunity performance of two types of operational amplifier. The results confirm the feasibility of the proposed method.

Correlation between equivalent input noise generators

Correlation between equivalent input voltage and current noise sources is usually considered to be unimportant by low-frequency circuit designers. This paper shows that measurements of noise figure as a function of source resistance make it possible to determine the spectral densities of the equivalent input noise generators and the correlation between them. Measurements were made on five different types of operational amplifier and considerable correlation was found in three of these.

Approximating the universal active element

The classification of universal amplifiers presented in this paper places all operational amplifiers and current conveyors known from the literature into a common framework, together with abstract concepts such as the universal active element and the nullor. Our approach is new in that we base it on four-terminal theory, which results in a classification that is more extensive but not more complex than classifications derived using two-port theory. It turns out that our classification contains a new type of operational amplifier, which we call current-feedback operational transconductance amplifier (CFB OTA), and also a new class of voltage-inverting current conveyors. We then demonstrate that our classification is very closely related to integrated-amplifier design by showing how all operational amplifiers and current conveyors can be implemented in CMOS using only a few CMOS circuits. Since the basic ideas behind CMOS and bipolar circuits are very similar, this paper is not process specific and can be seen as an attempt to bridge the gap between amplifier theory and amplifier design that has become ever wider in the past few years.

Relaxation of operational amplifier parameters after pulsed electron beam irradiation

The relaxation of operational amplifier parameters (offset voltage and differential gain) with time after pulsed electron beam irradiation has been studied as a function of total dose and amplifier type. Four types of operational amplifiers were studied viz., general purpose bipolar input (μA 741), super-beta transistor input (LM 308), JFET input (LF 356) and MOSFET input (CA 3140) from different vendors. The experiments were carried out mainly using 500 ns pulses from a Linear Accelerator. The study, the first of its kind, shows that while the electrical transient at the output of the operational amplifier recovers in a few milliseconds, relaxation of parameters can take several to several tens of seconds. This relaxation is attributed to the build up and/or anneal of damage in the oxide or at the interface of the internal transistor structures. The change and relaxation of parameters depend on operational amplifier type and total dose, and can have significant effects in certain application domains as illustrated by the response of a thermocouple amplifier after pulsed irradiation.

Low-noise state-space realisation of bandpass active filter

An active 2nd-order bandpass state-space filter realisation known as the symmetric-form filter has been studied theoretically and practically and has been found to have desirable qualities, particularly those of low noise and good linearity. The noise and linearity performance of this realisation has been compared with that of the companion-form filter (feedforward filter).5.7 The dynamic range of the symmetric form, expressed as a power ratio, is shown to be 1000 times greater than that of the companion form having the same transfer function and using the same type of operational amplifier.

The Application of Operational Amplifiers to Hardened Systems

Methods are described for evaluating neutron damage in the types of operational amplifiers that are typically used in modern tactical systems. Critical electrical parameters are discussed, and the internal current sources are identified as important control parameters for hardness assurance. These current sources are more important than internal transistor gain in determining internal operating margins of many linear circuit types. Damage factor variability is compared with digital devices, and potential hardness assurance approaches are discussed.

Signal-flowgraph representation of electronic-amplifier networks

It is shown that the basic action of the differential-input earthed-output type of operational amplifier may be given a flowgraph representation with a type of graph that is more general than those of Coates and Mason. Examples of embedded amplifiers are given to show the use of these graphs for the analysis of particular amplifier circuits.

Application of operational amplifiers to magnetic measurements

The method of voltage integration using expensive stabilized high-gain and low-drift amplifiers has been previously described. Many low-price general-purpose amplifiers are now available, and their performance as voltage integrators (fluxmeters) is reported. The fluxmeter is intended for general use in factory test rooms where measurements consist of a single flux change over a few seconds unlike recording hysteresigraphs, where integration may be over several minutes, and where output voltage drift problems may arise. These electronic fluxmeters offer advantages over the conventional moving coil fluxmeter in that zero return is very fast and that they are particularly suited to pass-fail testing when used in conjunction with a reference voltage source and a voltage comparator. Both a reference source and a comparator can be constructed using similar types of operational amplifiers.

Active nonreciprocal 2-port network synthesis with operational-amplifier realisations

An equivalent circuit of the general 2-port network based on a controlled source having two independent control voltages is derived. A synthesis procedure is given in terms of the transmission-matrix parameters, and it is shown that the network may be realised with only one type of operational amplifier. The method is applied to the ideal transformer, power amplifier and gyrator.