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97-623: Additional letter classes are defined for special-purpose amplifiers, with additional active elements, power supply improvements, or output tuning; sometimes a new letter symbol is also used by a manufacturer to promote its proprietary design. By December 2010, AB and D classes dominated nearly all of audio amplifier market with the former being favored in portable music players, home audio and cell phone owing to lower cost of class AB chips. Power amplifier circuits (output stages) are classified as A, B, AB and C for linear designs—and class D and E for switching designs. The classes are generally based on

194-418: A bipolar junction transistor is shown as the amplifying device. However, the same attributes are found with MOSFETs or vacuum tubes . In a class-A amplifier, 100% of the input signal is used (conduction angle θ = 360°). The active element remains conducting all of the time. Amplifying devices operating in class A conduct over the entire range of the input cycle. A class-A amplifier is distinguished by

291-593: A digital-to-analog converter (DAC) to convert the signal to analog form first. If the signal source is in digital form, such as in a digital media player or computer sound card , the digital circuitry can convert the binary digital signal directly to a pulse-width modulation signal that is applied to the amplifier, simplifying the circuitry considerably and reducing opportunities for noise ingress. A class-D amplifier with moderate output power can be constructed using regular CMOS logic process, making it suitable for integration with other types of digital circuitry. Thus it

388-461: A 20% yield) and as a result the price remained extremely high. When it was released in 1954, the Regency TR-1 cost $ 49.95 (equivalent to $ 567 today) and sold about 150,000 units. Raytheon and Zenith Electronics transistor radios soon followed and were priced even higher. In 1955, Raytheon's 8-TR-1 was priced at $ 80 (equivalent to $ 910 today). By November 1956 a transistor radio small enough to wear on

485-520: A bandwidth of no higher than 150 Hz, switching speed for the amplifier does not have to be as high as for a full range amplifier, allowing simpler designs. Class-D amplifiers for driving subwoofers are relatively inexpensive in comparison to class-AB amplifiers. The letter D used to designate this amplifier class is simply the next letter after C and, although occasionally used as such, does not stand for digital . Class-D and class-E amplifiers are sometimes mistakenly described as "digital" because

582-422: A circuit. Above that limit, the output ceases to scale in magnitude with the input, failing the definition of linearity. Transistor radio A transistor radio is a small portable radio receiver that uses transistor -based circuitry. Previous portable radios used vacuum tubes , which were bulky, fragile, had a limited lifetime, consumed excessive power and required large heavy batteries. Following

679-465: A class AB with just the 80 V supplies in place of the 40 V supplies, the T1 and T3 transistors would need to be in conduction throughout the 0 V to 80 V signal with the corresponding losses all through the wave period - not just the brief high energy bursts. To achieve this rail tracking control, T2 and T4 act as current amplifiers, each in series with its low voltage counterpart T1 and T3. The purpose of T2 and T3

776-474: A class-C amplifier, less than 50% of the input signal is used (conduction angle θ < 180°). Distortion is high and practical use requires a tuned circuit as load. Efficiency can reach 80% in radio-frequency applications. The usual application for class-C amplifiers is in RF transmitters operating at a single fixed carrier frequency , where the distortion is controlled by a tuned load on the amplifier. The input signal

873-452: A class-D amplifier's lower losses permit the use of smaller heat sinks for the MOSFETs while also reducing the amount of input power required, allowing for a lower-capacity power supply design. Therefore, class-D amplifiers are typically smaller than an equivalent class-AB amplifier. Another advantage of the class-D amplifier is that it can operate from a digital signal source without requiring

970-427: A class-D amplifier, the output filter blocks all harmonics; i.e., the harmonics see an open load. So even small currents in the harmonics suffice to generate a voltage square wave. The current is in phase with the voltage applied to the filter, but the voltage across the transistors is out of phase. Therefore, there is a minimal overlap between current through the transistors and voltage across the transistors. The sharper

1067-511: A combination mixer-oscillator, one as an audio amplifier, and two as intermediate-frequency amplifiers." One year after the release of the TR-1 sales approached the 100,000 mark. The look and size of the TR-1 were well received, but with only four transistors the sound quality was poor, and the reviews of the TR-1's performance were typically adverse. The Regency TR-1 was patented by Richard C. Koch, former Project Engineer of I.D.E.A. In February 1955,

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1164-708: A common shirt pocket. The TR-63 was the first transistor radio to sell in the millions, leading to the mass-market penetration of transistor radios. The TR-63 went on to sell seven million units worldwide by the mid-1960s. With the visible success of the TR-63, Japanese competitors such as Toshiba and Sharp Corporation joined the market. By 1959, in the United States market, there were more than six million transistor radio sets produced by Japanese companies that represented $ 62 million in revenue. The success of transistor radios led to transistors replacing vacuum tubes as

1261-475: A continuous fashion, respectively) following the input signal. Wasted heat on the output devices can be reduced as excess voltage is kept to a minimum. The amplifier that is fed with these rails itself can be of any class. These kinds of amplifiers are more complex, and are mainly used for specialized applications, such as very high-power units. Also, class-E and class-F amplifiers are commonly described in literature for radio-frequency applications where efficiency of

1358-423: A fixed amplitude, the switching elements (usually MOSFETs , but vacuum tubes and bipolar transistors have also been used) are switched completely on or completely off, rather than operating in linear mode. A MOSFET generally operates with the lowest on-state resistance when fully on and thus (excluding when fully off) has the lowest power dissipation when in that condition. Compared to an equivalent class-AB device,

1455-447: A full description of class-E operation may be found in the 1964 doctoral thesis of Gerald D. Ewing. Interestingly, analytical design equations only recently became known. In push–pull amplifiers and in CMOS, the even harmonics of both transistors just cancel. Experiment shows that a square wave can be generated by those amplifiers. Theoretically square waves consist of odd harmonics only. In

1552-519: A low voltage high current source to power the filaments of the tubes and high voltage for the anode potential typically required two batteries. Vacuum tubes were also inefficient and fragile compared to transistors and had a limited lifetime. Bell Laboratories demonstrated the first transistor on December 23, 1947. The scientific team at Bell Laboratories responsible for the solid-state amplifier included William Shockley , Walter Houser Brattain , and John Bardeen After obtaining patent protection,

1649-408: A matched temperature coefficient.) Another approach (often used with thermally tracking bias voltages) is to include small value resistors in series with the emitters. Class AB sacrifices some efficiency over class B in favor of linearity, thus is less efficient (below 78.5% for full-amplitude sine waves in transistor amplifiers, typically; much less is common in class-AB vacuum-tube amplifiers). It

1746-421: A parallel-tuned circuit consisting of an inductor and capacitor in parallel, whose components are chosen to resonate at the frequency of the input signal. Power can be coupled to a load by transformer action with a secondary coil wound on the inductor. The average voltage at the collector is then equal to the supply voltage, and the signal voltage appearing across the tuned circuit varies from near zero to near twice

1843-407: A public with disposable income amidst a period of prosperity, and the growing popularity of rock 'n' roll music. The influence of the transistor radio during this period is shown by its appearance in popular films, songs, and books of the time, such as the movie Lolita . Inexpensive transistor radios running on batteries enabled many in impoverished rural areas to become regular radio listeners for

1940-403: A related modulation technique before being applied to the amplifier. The time average power value of the pulses is directly proportional to the analog signal, so after amplification the signal can be converted back to an analog signal by a passive low-pass filter . The purpose of the output filter is to smooth the pulse stream to an analog signal, removing the high-frequency spectral components of

2037-580: A single number (resistance, capacitance, inductance, respectively). In contrast, a nonlinear element 's behavior is specified by its detailed transfer function , which may be given by a curved line on a graph. So specifying the characteristics of a nonlinear circuit requires more information than is needed for a linear circuit. "Linear" circuits and systems form a separate category within electronic manufacturing. Manufacturers of transistors and integrated circuits often divide their product lines into 'linear' and 'digital' lines. "Linear" here means " analog ";

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2134-444: A tuned reactive network between the switch and the load. The circuit obtains high efficiency by only operating the switching element at points of zero current (on to off switching) or zero voltage (off to on switching) which minimizes power lost in the switch, even when the switching time of the devices is long compared to the frequency of operation. The class-E amplifier is frequently cited to have been first reported in 1975. However,

2231-403: Is a sound system . The superposition principle, the defining equation of linearity, is equivalent to two properties, additivity and homogeneity , which are sometimes used as an alternate definition That is, a linear circuit is a circuit in which (1) the output when a sum of two signals is applied is equal to the sum of the outputs when the two signals are applied separately, and (2) scaling

2328-517: Is also sinusoidal with frequency f . A linear circuit with constant component values is called linear time-invariant (LTI). Informally, a linear circuit is one in which the electronic components ' values (such as resistance , capacitance , inductance , gain , etc.) do not change with the level of voltage or current in the circuit. Linear circuits are important because they can amplify and process electronic signals without distortion . An example of an electronic device that uses linear circuits

2425-451: Is because the D1 and D3 diodes which are intended to provide a path for the output voltage back into the upper devices are always reverse biased. They are drawn backwards. In place of these diodes, a voltage amplifier with gain which uses vout as its input would be needed in an actual design. There is another reason for this gain requirement between vout and T2 base in an actual class H design and that

2522-673: Is commonly found in System-on-Chips with integrated audio when the amplifier shares a die with the main processor or DSP. While class-D amplifiers are widely used to control motors , they are also used as power amplifiers. Though if the signal is not already in a pulse modulated format prior to amplification, it must first be converted, which may require additional circuitry. Switching power supplies have even been modified into crude class-D amplifiers (though typically these only reproduce low-frequencies with acceptable accuracy). High-quality class-D audio power amplifiers are readily available on

2619-423: Is done by modulating the supply rails so that the rails are only a few volts larger than the output signal "tracking" it at any given time. The output stage operates at its maximum efficiency all the time. This is due to the circuit ability to keep the rail transistors (T2 and T4) in cutoff until a music voltage peak is of a sufficient magnitude to require the additional voltage from the + and - 80 V supplies. Refer to

2716-487: Is low efficiency and high heat dissipation. In a class-B amplifier, the active device conducts for 180 degrees of the cycle (conduction angle θ = 180°). Because only half the waveform is amplified, significant harmonic distortion is directly present in the output signal. Therefore, class-B amplifiers are generally operated with tuned loading - where harmonics are shorted to ground by a series of resonators. Another method of reducing distortion, especially at audio frequencies,

2813-426: Is mostly in the first harmonic, it looks like a sine. That means that in the middle of the square the maximum of current has to flow, so it may make sense to have a dip in the square or in other words to allow some overswing of the voltage square wave. A class-F load network by definition has to transmit below a cutoff frequency and reflect above. Any frequency lying below the cutoff and having its second harmonic above

2910-403: Is no longer related directly to the input signal but instead varies in pulse width. In the class-D amplifier the active devices (transistors) function as electronic switches instead of linear gain devices; they are either on or off. The analog signal is converted to a stream of pulses that represents the signal by pulse-width modulation , pulse-density modulation , delta-sigma modulation or

3007-399: Is no signal) makes a large difference to the level of distortion (and to the risk of thermal runaway , which may damage the devices). Often, bias voltage applied to set this quiescent current must be adjusted with the temperature of the output transistors. (For example, in the circuit shown at right, the diodes would be mounted physically close to the output transistors, and specified to have

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3104-404: Is not the same as that of straight-line graphs . In the common case of a circuit in which the components' values are constant and don't change with time, an alternate definition of linearity is that when a sinusoidal input voltage or current of frequency f is applied, any steady-state output of the circuit (the current through any component , or the voltage between any two points)

3201-628: Is poor and heat is generated in the transistor. Class-A power amplifier designs have largely been superseded by more efficient designs, though their simplicity makes them popular with some hobbyists. There is a market for expensive high fidelity class-A amps considered a "cult item" among audiophiles mainly for their absence of crossover distortion and reduced odd-harmonic and high-order harmonic distortion . Class A power amplifiers are also used in some "boutique" guitar amplifiers due to their unique tonal quality and for reproducing vintage tones. Some hobbyists who prefer class-A amplifiers also prefer

3298-407: Is the push–pull stage , such as the very simplified complementary pair arrangement shown at right. Complementary devices are each used for amplifying the opposite halves of the input signal, which is then recombined at the output. This arrangement gives good efficiency, but usually suffers from the drawback that there is a small mismatch in the cross-over region – at the "joins" between

3395-461: Is to allow back-biasing diode D2 when the amplifier output is at a positive peak (above 39.3 V) and back biasing D4 when the output is at negative peak less than -39.3 V. During the musical peaks from 100 to 400 watts, the +/-40 V rails source no current as all the current comes from the +/-80 V rails. This figure is too simplistic, however, as it will not actually control the T2 and T4 transistors at all. This

3492-505: Is to assure that the signal applied to the T2 is always "ahead" of the Vout signal so it can never "catch up" with the rail tracker. The rail tracker amplifier might have a 50 V/μs slew rate while the AB amplifier might have only a 30 V/μs slew rate in order to guarantee this. Linear circuit A linear circuit is an electronic circuit which obeys the superposition principle . This means that

3589-399: Is to use two transistor devices in a push-pull configuration. Each conducts for one half (180°) of the signal cycle, and the device currents are combined so that the load current is continuous. At radio frequency , if the coupling to the load is via a tuned circuit , a single device operating in class B can be used because the stored energy in the tuned circuit supplies the "missing" half of

3686-476: Is typically much more efficient than class A. A vacuum tube amplifier design will sometimes have an additional suffix number for the class, for example, class B1. A suffix 1 indicates that grid current does not flow during any part of the input waveform, where a suffix 2 indicates grid current flows for part of the input waveform. This distinction affects the design of the driver stages for the amplifier. Suffix numbers are not used for semiconductor amplifiers. In

3783-406: Is used to switch the active device, causing pulses of current to flow through a tuned circuit forming part of the load. The class-C amplifier has two modes of operation: tuned and untuned. The diagram shows a waveform from a simple class-C circuit without the tuned load. This is called untuned operation, and the analysis of the waveforms shows the massive distortion that appears in the signal. When

3880-542: The Wall Street Journal . Chrysler made the all-transistor car radio, Mopar model 914HR, available as an "option" in fall 1955 for its new line of 1956 Chrysler and Imperial cars, which hit the showroom floor on October 21, 1955. The all-transistor car radio was a $ 150 option (equivalent to $ 1,710 in 2023). While on a trip to the United States in 1952, Masaru Ibuka , founder of Tokyo Telecommunications Engineering Corporation (now Sony ), discovered that AT&T

3977-600: The boombox and the Sony Walkman , and later on by digitally-based devices with higher audio quality such as portable CD players , personal audio players , MP3 players and (eventually) by smartphones , many of which contain FM radios. A transistor is a semiconductor device that amplifies and acts as an electronic switch. Before the transistor was invented, radios used vacuum tubes . Although portable vacuum tube radios were produced, they were typically bulky and heavy. The need for

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4074-478: The invention of the transistor in 1947—which revolutionized the field of consumer electronics by introducing small but powerful, convenient hand-held devices—the Regency TR-1 was released in 1954 becoming the first commercial transistor radio. The mass-market success of the smaller and cheaper Sony TR-63, released in 1957, led to the transistor radio becoming the most popular electronic communication device of

4171-562: The "non-saturated" region), and other "linear" circuit elements . Some examples of nonlinear electronic components are: diodes , transistors , and iron core inductors and transformers when the core is saturated. Some examples of circuits that operate in a nonlinear way are mixers , modulators , rectifiers , radio receiver detectors and digital logic circuits. Linear time-invariant circuits are important because they can process analog signals without introducing intermodulation distortion . This means that separate frequencies in

4268-416: The 1960s and 1970s. Transistor radios are still commonly used as car radios . Billions of transistor radios are estimated to have been sold worldwide between the 1950s and 2012. The pocket size of transistor radios sparked a change in popular music listening habits, allowing people to listen to music anywhere they went. Beginning around 1980, however, cheap AM transistor radios were superseded initially by

4365-486: The American market and the grand total of electronic products exported from Japan in 1958 increased 2.5 times in comparison to 1957. In August 1955, while still a small company, Tokyo Telecommunications Engineering Corporation introduced their TR-55 five-transistor radio under the new brand name Sony . With this radio, Sony became the first company to manufacture the transistors and other components they used to construct

4462-567: The RCA 6-BX-63 tube radio, the latter used $ 38 of batteries over the same time that the 8-TP-1 used 60 cents. In July 1955 the first positive review of a transistor radio appeared in the Consumer Reports . Noting the 8-TP-1's high sound quality and very low battery cost, the magazine stated that "The transistors in this set have not been used in an effort to build the smallest radio on the market, and good performance has not been sacrificed". Following

4559-522: The TR-63 had a small tuning capacitor and required a new battery design to produce the proper voltage. It used the nine-volt battery , which would become the standard for transistor radios. Approximately 100,000 units of the TR-63 were imported in 1957. This "pocketable" (the term "pocketable" was a matter of some interpretation, as Sony allegedly had special shirts made with oversized pockets for their salesmen) model proved highly successful. This should be treated with caution. A restored Sony TR63 readily fits

4656-489: The Tuna -shaped" radios could be purchased from Star-Kist for an insignificant amount of money giving their company visibility amongst the public. These novelty radios are now bought and sold as collectors' items amongst modern-day collectors. Since the 1980s, the popularity of radio-only portable devices declined with the rise of portable audio players which allowed users to carry and listen to tape-recorded music. This began in

4753-417: The U.S. Navy and I.D.E.A. built home television antenna boosters. The two companies worked together on the TR-1, looking to grow revenues for their respective companies by breaking into this new product area. In May 1954, Texas Instruments had designed and built a prototype and was looking for an established radio manufacturer to develop and market a radio using their transistors. The Chief Project Engineer for

4850-427: The accuracy of the bias in low cost op-amps such as the "741" may result in class A or class AB or class B performance, varying from device to device or with temperature). They are sometimes used as medium-power, low-efficiency, and high-cost audio power amplifiers. The power consumption is unrelated to the output power. At idle (no input), the power consumption is essentially the same as at high output volume. The result

4947-429: The amplifier. Such amplifiers have an efficiency around 60%. When Class-B amplifiers amplify the signal with two active devices, each operates over one half of the cycle. Efficiency is much improved over class-A amplifiers. Class-B amplifiers are also favoured in battery-operated devices, such as transistor radios . Class B has a maximum theoretical efficiency of π/4 (≈ 78.5%). A practical circuit using class-B elements

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5044-449: The company held a news conference on June 30, 1948, at which a prototype transistor radio was demonstrated. There are many claimants to the title of the first company to produce practical transistor radios, often incorrectly attributed to Sony (originally Tokyo Telecommunications Engineering Corporation). Texas Instruments had demonstrated all-transistor AM (amplitude modulation) radios as early as May 25, 1954, but their performance

5141-405: The cutoff can be amplified, that is an octave bandwidth. On the other hand, an inductive-capacitive series circuit with a large inductance and a tunable capacitance may be simpler to implement. By reducing the duty cycle below 0.5, the output amplitude can be modulated. The voltage square waveform degrades, but any overheating is compensated by the lower overall power flowing. Any load mismatch behind

5238-405: The device was much smaller, required far less power to operate than a tube radio, and was more resistant to physical shock. Since the transistor's base element draws current, its input impedance is low in contrast to the high input impedance of the vacuum tubes. It also allowed "instant-on" operation, since there were no filaments to heat up. The typical portable tube radio of the fifties was about

5335-410: The dominant electronic technology in the late 1950s. The transistor radio went on to become the most popular electronic communication device of the 1960s and 1970s. Billions of transistor radios are estimated to have been sold worldwide between the 1950s and 2012. Prior to the Regency TR-1, transistors were difficult to produce. Only one in five transistors that were produced worked as expected (only

5432-428: The edges, the lower the overlap. While in class D, transistors and the load exist as two separate modules, class F admits imperfections like the parasitics of the transistor and tries to optimise the global system to have a high impedance at the harmonics. Of course there must be a finite voltage across the transistor to push the current across the on-state resistance. Because the combined current through both transistors

5529-444: The filter can only act on the first harmonic current waveform, clearly only a purely resistive load makes sense, then the lower the resistance, the higher the current. Class F can be driven by sine or by a square wave, for a sine the input can be tuned by an inductor to increase gain. If class F is implemented with a single transistor, the filter is complicated to short the even harmonics. All previous designs use sharp edges to minimise

5626-660: The first time. Music broadcast from New Orleans and received in Jamaica through transistor radios inspired the development of ska, and less directly, reggae music. In the late 1950s, transistor radios took on more elaborate designs as a result of heated competition. Eventually, transistor radios doubled as novelty items. The small components of transistor radios that became smaller over time were used to make anything from " Jimmy Carter Peanut-shaped" radios to "Gun-shaped" radios to " Mork from Ork Eggship-shaped" radios. Corporations used transistor radios to advertise their business. " Charlie

5723-562: The input signal x ( t ) {\displaystyle x(t)} by a factor h {\displaystyle h} scales the output signal F ( x ( t ) ) {\displaystyle F(x(t))} by the same factor. A linear circuit is one that has no nonlinear electronic components in it. Examples of linear circuits are amplifiers , differentiators , and integrators , linear electronic filters , or any circuit composed exclusively of ideal resistors , capacitors , inductors , op-amps (in

5820-457: The linear line includes integrated circuits designed to process signals linearly, such as op-amps , audio amplifiers , and active filters , as well as a variety of signal processing circuits that implement nonlinear analog functions such as logarithmic amplifiers, analog multipliers , and peak detectors. Nonlinear elements such as transistors tend to behave linearly when small AC signals are applied to them. So in analyzing many circuits where

5917-438: The market. Dynamic range of 118 dB in a high-end consumer product was seen in the year 2009. Most, however, remain closer to 100 dB dynamic range at this time [2022] due to practical cost considerations. These designs have been said to rival traditional class A and AB amplifiers in terms of quality. An early use of class-D amplifiers was high-power subwoofer amplifiers in cars. Because subwoofers are generally limited to

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6014-449: The music signal is between 100 and 400 watts output. The key to understanding this efficiency without churning the actual numbers is that we have a 400-watt-capable amplifier but with the efficiency of a 100-watt amplifier. This is because the waveforms of music contain long periods under 100 watts and contain only brief bursts of up to 400 watts – in other words, the losses at 400 watts are for brief time periods. If this example were drawn as

6111-519: The opportunity to manufacture the TR-1, predicting sales of the transistor radios at "20 million radios in three years". The Regency TR-1 was announced on October 18, 1954, by the Regency Division of I.D.E.A., was put on sale in November 1954 and was the first practical transistor radio made in any significant numbers. Billboard reported in 1954 that "the radio has only four transistors. One acts as

6208-405: The output of the circuit F(x) when a linear combination of signals ax 1 (t) + bx 2 (t) is applied to it is equal to the linear combination of the outputs due to the signals x 1 (t) and x 2 (t) applied separately: It is called a linear circuit because the output voltage and current of such a circuit are linear functions of its input voltage and current. This kind of linearity

6305-414: The output stage devices being biased for class A operation. Subclass A2 is sometimes used to refer to vacuum-tube class-A stages that drive the grid slightly positive on signal peaks for slightly more power than normal class A (A1; where the grid is always negative). This, however, incurs higher signal distortion. Because transistors biased for class A essentially always have drain current, their efficiency

6402-434: The output waveform superficially resembles a pulse-train of digital symbols, but a class-D amplifier merely converts an input waveform into a continuously pulse-width modulated analog signal. (A digital waveform would be pulse-code modulated .) Other amplifier classes are mainly variations of the previous classes. For example, class-G and class-H amplifiers are marked by variation of the supply rails (in discrete steps or in

6499-743: The overlap. There are a variety of amplifier designs that enhance class-AB output stages with more efficient techniques to achieve greater efficiency with low distortion. These designs are common in large audio amplifiers since the heatsinks and power transformers would be prohibitively large (and costly) without the efficiency increases. The terms "class G" and "class H" are used interchangeably to refer to different designs, varying in definition from one manufacturer or paper to another. Class-G amplifiers (which use "rail switching" to decrease power consumption and increase efficiency) are more efficient than class-AB amplifiers. These amplifiers provide several power rails at different voltages and switch between them as

6596-411: The proper load (e.g., an inductive-capacitive filter plus a load resistor) is used, two things happen. The first is that the output's bias level is clamped with the average output voltage equal to the supply voltage. This is why tuned operation is sometimes called a clamper . This restores the waveform to its proper shape, despite the amplifier having only a one-polarity supply. This is directly related to

6693-404: The proportion of each input cycle (conduction angle) during which an amplifying device passes current. The image of the conduction angle derives from amplifying a sinusoidal signal. If the device is always on, the conducting angle is 360°. If it is on for only half of each cycle, the angle is 180°. The angle of flow is closely related to the amplifier power efficiency . In the illustrations below,

6790-404: The pulses. The frequency of the output pulses is typically ten or more times the highest frequency in the input signal to amplify, so that the filter can adequately reduce the unwanted harmonics and accurately reproduce the input. The main advantage of a class-D amplifier is power efficiency. Efficiency over 90% is achievable with MOSFETs and >80% is fairly common. Because the output pulses have

6887-615: The qualitative behavior of the circuit, characterizing it using terms such as gain , phase shift , resonant frequency , bandwidth , Q factor , poles , and zeros . The analysis of a linear circuit can often be done by hand using a scientific calculator . In contrast, nonlinear circuits usually do not have closed form solutions. They must be analyzed using approximate numerical methods by electronic circuit simulation computer programs such as SPICE , if accurate results are desired. The behavior of such linear circuit elements as resistors, capacitors, and inductors can be specified by

6984-575: The radio design at Texas Instruments' headquarters in Dallas, Texas was Paul D. Davis Jr., who had a degree in Electrical Engineering from Southern Methodist University. He was assigned the project due to his experience with radio engineering in World War II. None of the major radio makers including RCA, GE, Philco, and Emerson were interested. The President of I.D.E.A. at the time, Ed Tudor, jumped at

7081-531: The radio. The TR-55 was also the first transistor radio to utilize all miniature components. It's estimated that only 5,000 to 10,000 units were produced. The TR-63 was introduced by Sony to the United States in December 1957. The TR-63 was 6 mm ( 1 ⁄ 4  in) narrower and 13 mm ( 1 ⁄ 2  in) shorter than the original Regency TR-1. Like the TR-1 it was offered in four colors: lemon, green, red, and black. In addition to its smaller size,

7178-517: The same time as transistor radios. Parents found that purchasing a small transistor radio was a way for children to listen to their music without using the family tube radio. Sony and other Japanese companies were much faster than Americans to focus on stylish, pocket-sized radios for the youth market, helping them to dominate the radio market. American companies began using lower-cost Japanese components but their radios were less attractive or sophisticated. By 1964 no transistor radio with only US components

7275-434: The same way as in class B over half the waveform, but also conducts a small amount on the other half. As a result, the region where both devices simultaneously are nearly off (the "dead zone") is reduced. The result is that when the waveforms from the two devices are combined, the crossover is greatly minimised or eliminated altogether. The exact choice of quiescent current (the standing current through both devices when there

7372-467: The schematic figure. The class H amplifier can actually be thought of as two amplifiers in series. In the schematic example shown by the figure, +/- 40 V rail amplifiers can produce about 100 watts continuous into an 8-ohm load. If the output signal is operating below 40 volts, the amplifier only has the losses associated with a 100 W amplifier. This is because the Class H upper devices T2 and T4 are only used when

7469-429: The second phenomenon: the waveform on the center frequency becomes less distorted. The residual distortion is dependent upon the bandwidth of the tuned load, with the center frequency seeing very little distortion, but greater attenuation the farther from the tuned frequency that the signal gets. The tuned circuit resonates at one frequency, the fixed carrier frequency, and so the unwanted frequencies are suppressed, and

7566-469: The second transistor radio, the 8-TP-1, was introduced by Raytheon . It was larger than the TR-1, including a four-inch speaker and eight transistors, four more than the TR-1, so the sound quality was much better. An additional benefit of the 8-TP-1 was its efficient battery consumption; the 8-TP-1 cost 1/6 cent per hour to operate, while the TR-1 cost 40 times as much. While the Raytheon radio cost $ 30 more than

7663-474: The signal levels are small, for example those in TV and radio receivers, nonlinear elements can be replaced with a linear small-signal model , allowing linear analysis techniques to be used. Conversely, all circuit elements, even "linear" elements, show nonlinearity as the signal level is increased. If nothing else, the power supply voltage to the circuit usually puts a limit on the magnitude of voltage output from

7760-442: The signal output approaches each level. Thus, the amplifier increases efficiency by reducing the wasted power at the output transistors. Class-G amplifiers are more efficient than class AB but less efficient when compared to class D, however, they do not have the electromagnetic interference effects of class D. Class-H amplifiers create an infinitely variable (analog) supply rail. They are sometimes referred to as rail trackers. This

7857-479: The signal stay separate and do not mix, creating new frequencies ( heterodynes ). They are also easier to understand and analyze. Because they obey the superposition principle , linear circuits are governed by linear differential equations , and can be analyzed with powerful mathematical frequency domain techniques, including Fourier analysis and the Laplace transform . These also give an intuitive understanding of

7954-417: The size and weight of a lunchbox and contained several heavy, non-rechargeable batteries—one or more so-called "A" batteries to heat the tube filaments and a large 45- to 90-volt "B" battery to power the signal circuits. By comparison, the transistor radio could fit in a pocket and weighed half a pound or less, and was powered by standard flashlight batteries or a single compact battery. The 9-volt battery

8051-470: The success of the 8-TP-1, Zenith, RCA, DeWald, Westinghouse, and Crosley produced many additional transistor radio models. The TR-1 remained the only shirt pocket-sized radio; rivals made "coat-pocket radios" that Consumer Reports also reviewed as not performing well. Chrysler and Philco announced that they had developed and produced the world's first all-transistor car radio in the April 28th 1955 edition of

8148-470: The supply voltage during the RF cycle. The input circuit is biased so that the active element (e.g., transistor) conducts for only a fraction of the RF cycle, usually one-third (120 degrees) or less. The active element conducts only while the collector voltage is passing through its minimum. By this means, power dissipation in the active device is minimised, and efficiency increased. Ideally, the active element would pass only an instantaneous current pulse while

8245-431: The traditional classes is important, yet several aspects deviate substantially from their ideal values. These classes use harmonic tuning of their output networks to achieve higher efficiency and can be considered a subset of class C due to their conduction-angle characteristics. The class-E amplifier is a highly efficient tuned switching power amplifier used at radio frequencies. It uses a single-pole switching element and

8342-530: The two active elements conducts more than half of the time. Class AB is widely considered a good compromise for amplifiers, since many types of input signal are nominally quiet enough to stay in the "class-A" region, where they are amplified with good fidelity, and by definition if passing out of this region, will be large enough that the distortion products typical of class B will be relatively small. The crossover distortion can be reduced further by using negative feedback . In class-AB operation, each device operates

8439-424: The two halves of the signal, as one output device has to take over supplying power exactly as the other finishes. This is called crossover distortion . An improvement is to bias the devices so they are not completely off when they are not in use. This approach is called class AB operation. In a class-AB amplifier, the conduction angle is intermediate between class A and B (conduction angle θ > 180°); each one of

8536-534: The use of thermionic valve (tube) designs instead of transistors, for several reasons: Transistors are much less expensive than tubes so more elaborate designs that use more parts are still less expensive to manufacture than tube designs. A classic application for a pair of class-A devices is the long-tailed pair , which is exceptionally linear, and forms the basis of many more complex circuits, including many audio amplifiers and almost all op-amps . Class-A amplifiers may be used in output stages of op-amps (although

8633-437: The voltage across it is zero: it then dissipates no power and 100% efficiency is achieved. However practical devices have a limit to the peak current they can pass, and the pulse must therefore be widened, to around 120 degrees, to obtain a reasonable amount of power, and the efficiency is then 60–70%. Class-D amplifiers use some form of pulse-width modulation to control the output devices. The conduction angle of each device

8730-454: The wanted full signal (sine wave) is extracted by the tuned load. The signal bandwidth of the amplifier is limited by the Q-factor of the tuned circuit but this is not a serious limitation. Any residual harmonics can be removed using a further filter. In practical class-C amplifiers a tuned load is invariably used. In one common arrangement the resistor shown in the circuit above is replaced with

8827-443: The waveform. Devices operating in Class B are used in linear amplifiers, so called because the radio frequency output power is proportional to the square of the input excitation voltage. This is more easily understood if stated as "output voltage is proportional to input voltage, thus ouput power is proportional to input power." This characteristic prevents distortion of amplitude-modulated or frequency-modulated signals passing through

8924-652: The wrist and a claimed battery life of 100 hours cost $ 29.95. Sony's TR-63, released in December 1957, cost $ 39.95 (equivalent to $ 434 today). Following the success of the TR-63 Sony continued to make their transistor radios smaller. Because of the extremely low labor costs in Japan, Japanese transistor radios began selling for as low as $ 25. By 1962, the TR-63 cost as low as $ 15 (equivalent to $ 151 today), which led to American manufacturers dropping prices of transistor radios down to $ 15 as well. Rock 'n roll music became popular at

9021-741: Was about to make licensing available for the transistor. Ibuka and his partner, physicist Akio Morita , convinced the Japanese Ministry of International Trade and Industry (MITI) to finance the $ 25,000 licensing fee (equivalent to $ 286,842 today). For several months Ibuka traveled around the United States borrowing ideas from the American transistor manufacturers. Improving upon the ideas, Tokyo Telecommunications Engineering Corporation made its first functional transistor radio in 1954. Within five years, Tokyo Telecommunications Engineering Corporation grew from seven employees to approximately five hundred. Other Japanese companies soon followed their entry into

9118-548: Was available; by the mid-1960s the Japanese radio components had also been supplanted by even less-expensive manufacturing in Korea, Taiwan, and Hong Kong. The Zenith Trans-Oceanic 7000 was, until 1970, the last transistor radio manufactured in the US. Transistor radios were extremely successful because of three social forces—a large number of young people due to the post–World War II baby boom ,

9215-410: Was introduced for powering transistor radios. Two companies working together, Texas Instruments of Dallas, and Industrial Development Engineering Associates (I.D.E.A.) of Indianapolis, Indiana, were behind the unveiling of the Regency TR-1 , the world's first commercially produced transistor radio. Previously, Texas Instruments was producing instrumentation for the oil industry and locating devices for

9312-473: Was never put into commercial production. RCA had demonstrated a prototype transistor radio as early as 1952, and it is likely that they and the other radio makers were planning transistor radios of their own, but Texas Instruments and Regency Division of I.D.E.A., were the first to offer a production model starting in October 1954. The use of transistors instead of vacuum tubes as the amplifier elements meant that

9409-635: Was well below that of equivalent vacuum tube models. A workable all-transistor radio was demonstrated in August 1953 at the Düsseldorf Radio Fair by the German firm Intermetall. It was built with four of Intermetall 's hand-made transistors, based upon the 1948 invention of the "Transistor"-germanium point-contact transistor by Herbert Mataré and Heinrich Welker . However, as with the early Texas Instruments units (and others) only prototypes were ever built; it

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