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An analog computer or analogue computer is a type of computer that uses the continuous variation aspect of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved. In contrast, digital computers represent varying quantities symbolically and by discrete values of both time and amplitude.
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal. It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a power gain greater than one.
An operational amplifier is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op amp produces an output potential that is typically 100,000 times larger than the potential difference between its input terminals. The operational amplifier traces its origin and name to analog computers, where they were used to perform mathematical operations in linear, non-linear, and frequency-dependent circuits.
In electronics, a comparator is a device that compares two voltages or currents and outputs a digital signal indicating which is larger. It has two analog input terminals and and one binary digital output . The output is ideally
An audio power amplifier is an electronic amplifier that amplifies low-power electronic audio signals, such as the signal from a radio receiver or an electric guitar pickup, to a level that is high enough for driving loudspeakers or headphones. Audio power amplifiers are found in all manner of sound systems including sound reinforcement, public address, home audio systems and musical instrument amplifiers like guitar amplifiers. It is the final electronic stage in a typical audio playback chain before the signal is sent to the loudspeakers.
An instrumentation amplifier is a type of differential amplifier that has been outfitted with input buffer amplifiers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment. Additional characteristics include very low DC offset, low drift, low noise, very high open-loop gain, very high common-mode rejection ratio, and very high input impedances. Instrumentation amplifiers are used where great accuracy and stability of the circuit both short- and long-term are required.
A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by solid state amplifiers in the 1960s and 1970s. Valve amplifiers can be used for applications such as guitar amplifiers, satellite transponders such as DirecTV and GPS, high quality stereo amplifiers, military applications and very high power radio and UHF television transmitters.
A differential amplifier is a type of electronic amplifier that amplifies the difference between two input voltages but suppresses any voltage common to the two inputs. It is an analog circuit with two inputs and and one output , in which the output is ideally proportional to the difference between the two voltages:
An integrator in measurement and control applications is an element whose output signal is the time integral of its input signal. It accumulates the input quantity over a defined time to produce a representative output.
This article illustrates some typical operational amplifier applications. A non-ideal operational amplifier's equivalent circuit has a finite input impedance, a non-zero output impedance, and a finite gain. A real op-amp has a number of non-ideal features as shown in the diagram, but here a simplified schematic notation is used, many details such as device selection and power supply connections are not shown. Operational amplifiers are optimised for use with negative feedback, and this article discusses only negative-feedback applications. When positive feedback is required, a comparator is usually more appropriate. See Comparator applications for further information.
A Norton amplifier or current differencing amplifier (CDA) is an electronic amplifier with two low impedance current inputs and one low impedance voltage output where the output voltage is proportional to the difference between the two input currents. A norton amplifier is a current controlled voltage source (CCVS) controlled by the difference of two input currents.
The Ibanez Tube Screamer (TS808/TS9) is a guitar overdrive pedal, made by Ibanez. The pedal has a characteristic mid-boosted tone popular with blues, rock and metal players. The Tube Screamer has been used by many guitarists to create their signature sound, and is one of the most successful, widely copied, and custom-modified ("modded") overdrive pedals in the history of the electric guitar.
The operational transconductance amplifier (OTA) is an amplifier whose differential input voltage produces an output current. Thus, it is a voltage controlled current source (VCCS). There is usually an additional input for a current to control the amplifier's transconductance. The OTA is similar to a standard operational amplifier in that it has a high impedance differential input stage and that it may be used with negative feedback.
A direct-coupled amplifier or DC amplifier is a type of amplifier in which the output of one stage of the amplifier is coupled to the input of the next stage in such a way as to permit signals with zero frequency, also referred to as direct current, to pass from input to output. This is an application of the more general direct coupling. It was invented by Harold J Paz and Francis P. Keiper Jr. in 1955. It displaced the triode vacuum tube amplifier designed by Lee de Forest. Almost all vacuum tube circuit designs are now replaced with direct coupled transistor circuit design. It is the first transistor amplifier design that did not include coupling capacitors. The direct-coupled amplifier allowed analog circuits to be built smaller with the elimination of coupling capacitors and removed the lower frequency limitation that is dependent on capacitors.
A fully differential amplifier (FDA) is a DC-coupled high-gain electronic voltage amplifier with differential inputs and differential outputs. In its ordinary usage, the output of the FDA is controlled by two feedback paths which, because of the amplifier's high gain, almost completely determine the output voltage for any given input.
In electronic systems, power supply rejection ratio (PSRR), also supply-voltage rejection ratio, is a term widely used to describe the capability of an electronic circuit to suppress any power supply variations to its output signal.
George A. Philbrick was responsible, through his company George A. Philbrick Researches (GAP/R), for the 1953 commercialization and wide adoption of operational amplifiers, a now-ubiquitous component of analog electronic systems, and the invention and commercialization of electronic analog computers based on the operational amplifier principle. He also created the first electronic training simulator, the Polyphemus. The invention, or co-invention, of the operational amplifier has also been credited to a number of other people, including a war-needs driven Bell Labs team led by Clarence A. Lovell and Loebe Julie.
Tube sound is the characteristic sound associated with a vacuum tube amplifier, a vacuum tube-based audio amplifier. At first, the concept of tube sound did not exist, because practically all electronic amplification of audio signals was done with vacuum tubes and other comparable methods were not known or used. After introduction of solid state amplifiers, tube sound appeared as the logical complement of transistor sound, which had some negative connotations due to crossover distortion in early transistor amplifiers. However, solid state amplifiers have been developed to be flawless and the sound is later regarded neutral compared to tube amplifiers. Thus the tube sound now means 'euphonic distortion.' The audible significance of tube amplification on audio signals is a subject of continuing debate among audio enthusiasts.
The current-feedback operational amplifier is a type of electronic amplifier whose inverting input is sensitive to current, rather than to voltage as in a conventional voltage-feedback operational amplifier (VFA). The CFA was invented by David Nelson at Comlinear Corporation, and first sold in 1982 as a hybrid amplifier, the CLC103. An early patent covering a CFA is U.S. Patent 4,502,020, David Nelson and Kenneth Saller. The integrated circuit CFAs were introduced in 1987 by both Comlinear and Elantec. They are usually produced with the same pin arrangements as VFAs, allowing the two types to be interchanged without rewiring when the circuit design allows. In simple configurations, such as linear amplifiers, a CFA can be used in place of a VFA with no circuit modifications, but in other cases, such as integrators, a different circuit design is required. The classic four-resistor differential amplifier configuration also works with a CFA, but the common-mode rejection ratio is poorer than that from a VFA.
The NE5532, also sold as SA5532, SE5532 and NG5532 is a dual monolithic, bipolar, internally compensated operational amplifier for audio applications introduced by Signetics in 1979. The 5532 and the contemporary TL072 were the first operational amplifiers that outperformed discrete class A circuits in professional audio applications. Due to low noise and very low distortion, the 5532 became the industry standard for professional audio. According to Douglas Self, "there is probably no music on the planet that has not passed through a hundred or more 5532s on its way to the consumer". The performance of the 5532 remained best in class for almost thirty years, until the introduction of the LM4562 in 2007. As of 2021, the 5532 remains in mass production as a generic product.
References
- ↑ Jung, Walt (2006). "Chapter 8: Op Amp History" (PDF). Op Amp Applications Handbook. Newnes. ISBN 9780750678445 . Retrieved 2012-12-27.
- ↑ Rostky, George (March 24, 1997). "Unsung Hero Pioneered Op Amp" (PDF). EE Times. Retrieved 2012-12-27., contains schematic diagram of the Julie op amp
- ↑ Pease, Bob (May 3, 1999). "What's All This Julie Stuff, Anyhow?". Electronic Design. Archived from the original on December 18, 2012. Retrieved 2012-12-27.