Audio amplifier design pdf

No Preview Available! July LM 1 Watt Audio Power Amplifier General Description The LM is an audio power amplifier primarily designed for demanding applications in mobile phones and other por- table communication device applications. Boomer audio power amplifiers were designed specifically to provide high quality output power with a minimal amount of external components. The LM does not require output coupling capacitors or bootstrap capacitors, and therefore is ideally suited for mobile phone and other low voltage appli- cations where minimal power consumption is a primary re- quirement.

===

We are searching data for your request:

Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Content:

• Csr8675 Schematic
• Design Resources
• HARMAN International
• Electrical Engineering design-build project: Class-D audio amplifier design and characterization
• Audio Power Amplifier Design Handbook
• Power amplifier design pdf
• audio power amplifier design handbook 3rd edition

WATCH RELATED VIDEO: Class AB Audio Amplifier

Csr8675 Schematic

Not only does he teach the fundamentals and details of power amplifier design per se but also discloses a systematic approach to analyse the distortion performance of typical amplifier topologies. The latter is particularly important as systematics does not appear to be a natural thing in audio circuit design at least if we consider many other publications which shall remain unnamed here.

Two years ago the 5 th edition of the Audio Power Amplifier Design Handbook has been published as the latest book by Self on this topic, and that s the text I m referring to below. In recent years I ve done considerable research in high performance and in particular low distortion amplifier topologies. This paper will highlight a couple of results from this research which complement or contrast with Self s writing.

I hope that this information will be found helpful for audio circuit designers and that it will contribute to the art of power amplifier design. For consistency with the Audio Power Amplifier Design Handbook I ve largely adopted Self s terminology even if I ve used a different nomenclature in other publications. The order of the topics discussed roughly follows the structure of Self s book. For ease of understanding, references to figures in the Audio Power Amplifier Design Handbook are noted as such by the addition of the corresponding page number in brackets.

The contributions ranged from literature suggestions, notes with regards to content, providing transistor samples to proof reading. This all is very much appreciated! This is because the output stage is not thought to be fundamental for the basic operation of the amplifier, although it surely is difficult to omit in most practical circumstances.

The difference in nomenclature might confuse some readers and should be mentioned. I might also add that the amplifier depicted in figure 5. As it happens this error partially cancels with the base current errors of the basic Widlar mirror when using the standard topology considered in Self s book. Pretty accurate cancellation which in the context of discrete design means: largely limited by transistor mismatch can be achieved by biasing the emitter follower within the VAS at a collector current equivalent to the tail current of the input pair.

If R5 is chosen such that Q1 and Q2 are operated at equal collector voltage and R3 and R4 have equal value the error introduced by the base current of Q5 is cancelled with the base current of Q6.

Overall this topology leads to very good input stage balance and offers low drift see e. The use of a Wilson or improved Wilson mirror will lead to worse collector current balance for the input stage, as the VAS base current error is not cancelled. However as noted by Self on page 85 these mirrors might contribute less distortion.

Another performance aspect of current mirrors is their noise contribution. As detailed in [2] this value is well below the minimum value required for good noise performance. At first it is counterintuitive that higher resistance values give lower noise, as for feedback networks and the emitter degeneration resistors of the input pair the opposite holds; however the noise contribution of the current mirror is in the form of a current, whereas the usual concern is voltage noise [3].

However the slope of the interpolated data suggests that we can t expect further drastic reductions in noise anyway. A pleasing result. As often there is however a caveat: on page Self notes that low current mirror emitter resistor values might be needed for best slew-rate performance, limiting the possible current mirror noise reduction. One possible fix for this is to add shunt capacitors in parallel with the emitter degeneration resistors; a value of 1 nf seems to be more than enough and does not compromise noise performance within the audio frequency range.

The reduction in transconductance which the degeneration resistors cause is accompanied by a proportional increase in sensitivity to current mirror noise. For an undegenerated bipolar input stage the detectable differences for the various emitter resistor values would be much lower. Current Feedback High-speed circuit designers will be very familiar with the concept of current feedback operational amplifiers.

In contrast to the ubiquituous voltage feedback amplifiers which are the main focus of the book by Self the current feedback amplifier class has the property of a closed-loop bandwidth which is to a good extent independent of closed-loop gain.

Additionally typical topologies have either strongly reduced or entirely absent first-order slew-rate limits. This is achieved by making the inverting input low impedance, hence sensitive to current rather than voltage; as a result the current available to charge the compensation capacitor may be proportional to the input signal which removes first-order slew-rate limitations and the compensation becomes proportional to the total feedback network resistance which achieves the constant bandwidth property.

More details on the theoretical fundamentals of current feedback amplifiers may be found in [4]. I noted that the Audio Power Amplifier Design Handbook doesn t consider the special properties of this amplifier class. In particular for the amplifier shown in figure 4.

According to equation 1 the closed-loop bandwidth of this amplifier is a meagre 72 khz 1, which is easily confirmed by simulation. It is hardly surprising that such an amplifier performs very poorly with respect to high-frequency distortion. To make a meaningful comparison to the standard voltage feedback architecture the compensation capacitor must be reduced to 10 pf or the feedback resistor scaled to 2. It is clear that this change will greatly improve the linearity of the amplifier, and it is no longer obvious if a differential pair with its even-order distortion product cancellation offers lower distortion.

The amplifier shown in figure 4 implements the current feedback principle with correct compensation. Also the resistive collector load of the input pair has been replaced with an active current source and a second current source has been added to reduce DC offset. From the measurements shown in figure 5 it is clear that this amplifier still has appreciable high-frequency distortion which will be relevant for a power amplifier. However distortion is almost two orders of magnitude lower than what Self measured for the singleended input stage see figure 4.

A tenfold reduction in distortion is explained by the increased loop gain; the additional distortion reduction is probably attributed to the increased input stage quiescent current and the use of an active load for the input stage. More elaborate current feedback amplifiers use complementary input stages; one such is depicted in figure 5.

Linearity of such an input stage is not easily compared to the more traditional differential pair because of its fundamentally different operation.

Also equation 1 shows that the bias conditions of the input stage have no first-order influence on loop gain; this implies that large-signal 6. The rise at frequencies below 20 Hz is due to the increasing oscillator residual contribution and not actual amplifier distortion. This is different for voltage feedback amplifiers because their loop gain is proportional to input stage transconductance.

Hence appreciable lower high-frequency distortion for current feedback amplifiers is expected. A final conclusion whether voltage or current feedback topologies are more suitable for audio power amplifier design cannot be given here, as reasonably accurate discussion of the various possible current feedback architectures would probably require several weeks of research and another twenty pages of writing.

By the very amount that global feedback is reduced by the compensation capacitor the local VAS feedback is increased. This in turn means that the total feedback applied to the VAS remains constant. Page suggests that VAS nonlinearity is a result of the basic exponential voltage-current transfer characteristics of bipolar transistors; as this characteristic can be expected to be largely independent of frequency as is the total feedback applied to reduce it as stated above we should expect the VAS distortion to be independent of frequency.

However figure 5. It is obvious that we have a contradiction here, and I d like to suggest that the exponential voltage-current transfer characteristic is not the main VAS distortion source. Page correctly states that the common-emitter VAS transistor is usually operated in a current-driven fashion. The exponential transfer characteristic of the VAS transistor surely sets the output voltage of the input stage current mirror as function of collector current. This however has no first-order effect on the amplifier linearity at least as long as we ignore the action of the compensation capacitor more on this later.

If it were a voltage-driven common-emitter stage this would reduce its gain and hence total amplifier open-loop gain below the dominant pole in proportion to the resistor value. Simulation quickly reveals that the amplifier open-loop gain remains more or less constant even with large emitter resistor values. This is further supported by measurements of the amplifier shown in figure 6.

Distortion has been measured with two different devices 2N and MJE for Q7 as shown in figure 7. If the basic exponential voltage-current relationship of the bipolar transistor were the dominant distortion mechanism then both transistors should give very much identical distortion performance. Minor differences might appear due to saturation current differences or log conformance deviations.

However the 6 times difference observed at 10 khz in the measurement appears to be well beyond the expected order of magnitude of these effects. Also the exponential voltage-current relationship gives no reason why one transistor should be superior at low frequencies while the other outperforms at high frequencies.

Different h F E or Early voltage of the transistors used might be a reason for the distortion deviations observed; higher h F E or Early voltage leads to higher open-loop gain below the dominant pole and more local VAS feedback. To confirm that this does not explain the distortion difference the DC open-loop gain was measured. The observed figures were The tiny difference of 0. It s probably most easy if I proceed by just stating the three main distortion mechanisms I ve been able to separate with the use of extensive simulation and measurement: Collector voltage dependent collector-base junction capacitance.

Early effect. Nonlinear modulation of compensation capacitor reference voltage. In the following I ll briefly discuss these three distortion mechanisms. It is well known that the collector-base junction capacitance of a transistor shows a dependence on collector voltage [10] and that this can cause 3 A detailed analysis [7] shows that a VAS emitter resistor reduces Early effect in the VAS transistor under certain conditions and hence can even increase open-loop gain.

Two different transistor types for Q7 were used. As the collector-base junction capacitance appears in parallel with the compensation capacitor it is clear that the open-loop gain above the dominant pole of the amplifier is modulated with output voltage. This necessarily modulates the closed-loop gain of the amplifier too, which is then observed as distortion. The asymmetric modulation of the junction capacitance suggests that the observed distortion must be mainly 2 nd harmonic which is found to be true for the circuit shown in figure 6.

Again this is found to be true as shown in figure 7. Note that this distortion source is not linearised by local feedback of the compensation capacitor. Rather this distortion mechanism distorts the feedback action itself by making the feedback network component i. It can hence only be linearised by global feedback. In my experience collector voltage dependent collector-base junction capacitance is typically the dominant distortion source for frequencies above 1 khz if a basic one-transistor VAS is used.

Clearly its magnitude is proportional to the collector-base junction capacitance value; the datasheets available at the time of writing [8][9] quote a maximum value of 6. It is reasonable to assume that typical values will have a ratio which is roughly similar to that of the maximum values, so 9 times higher distortion for the MJE is expected.

The measurements are in reasonable agreement with this figure. Finally it is worth considering the effect of increased supply voltages. As stated above, the collector-base capacitance is reduced at higher collector voltages.

Also for a given output level the modulation of the collector-base capacitance i. Hence it is reasonable to assume that distortion is reduced as well. This explains the improvement which has been observed with increased supply voltages in figure 5.

The measurements depicted in figure 7 show frequency-independent lowfrequency distortion floors which consist of a mixture of second and third harmonic distortion. This distortion is not explained by collector voltage dependent collector-base junction capacitance. However as the collector of the VAS transistor experiences large voltage swings Early effect is a strong candidate for the distortion source.

Their values are roughly proportional to Early voltage V A and inversely proportional to collector current I C : At low frequencies we can expect I C to stay almost constant with output voltage as the impedance of the compensation capacitor, the constant current source collector load and the output stage is rather high.

Design Resources

To browse Academia. Log in with Facebook Log in with Google. Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link. Need an account?

HARMAN International

This book is the essential reference for audio power amplifier designers and engineers. Author Douglas Self covers all the issues of distortion and linearity, power supplies, protection, reliability and layout. He also tackles unusual forms of compensation and unexpected sources of distortion such as capacitors and fuses. This much expanded and updated Fifth Edition includes four NEW chapters, one of them dedicated to the XD crossover-displacement principle, invented by the author, and used by Cambridge Audio. The book has a wealth of new material on four-stage amplifier architectures, current-mirrors, power transistors with internal sensing diodes, amplifier bridging, subtle distortion mechanisms, input stage common-mode distortion, double input stages, amplifier stability, output stages with gain, transformers and hum fields, inrush current suppression, DC servo design, thermal protection, the subtleties of cooling fan control, advanced line input stages, ultra-low-noise design, high and low-pass filtering, testing and safety, infra-red control, signal activation, 12V trigger, level indication and much more. There is significantly expanded material on professional power amplifiers as used in sound reinforcement and PA applications. This book is a must-have for audio power amplifier professionals and audiophiles, amateur constructors and anyone with intellectual curiosity about the struggle towards technical excellence. PThis book is the essential reference for audio power amplifier designers and engineers. Author Douglas Self covers all the issues of distortion and linearity. Kirimkan Ini lewat Email BlogThis!

Electrical Engineering design-build project: Class-D audio amplifier design and characterization

Picture of the book : 3…. Pro Arduino. Arduino Project Handbook Volume 1. Picture of the book: Arduino Pro….

Audio Power Amplifier Design Handbook

Two groups of twenty students complete it every semester working in teams of four members. The students of these two degrees and also those of the other three degrees taught at Telecom-BCN are asked to fulfill the design, implementation and verification of five blocks of a product specified by the faculty. The product in the last three years, with small variations every year, has been a campus-wide announcements distribution system using wireless communications. All students know the requirements and specifications of the whole product and of the interfaces between blocks and the students of each degree are assigned to design, implement and test only one of the blocks. In this paper, the design-build projects performed by the EE and AV students, which complement each other and are integrated at the end of the semester, are presented with enough detail to allow other institutions considering its implementation. Additionally to the practical aspects design guidelines, complexity, components and tools, cost, … , the learning outcomes and students achievements will also be presented.

Power amplifier design pdf

Douglas Self offers a tried and tested method for designing audio amplifiers in a way that improves performance at every point in the circuit where distortion can creep in without significantly increasing cost. His quest for the Blameless Amplifier takes readers through the causes of distortion, measurement techniques, and design solutions to minimise distortion and efficiency. The result is a book that is crammed with unique insights into audio design and performance, as well as complete amplifier designs and schematics. Whether you are a dedicated audiophile who wants to gain a more complete understanding of the design issues behind a truly great amp, or a professional electronic designer seeking to learn more about the art of amplifier design, Douglas Self's Handbook is the essential guide to design principles and practice. Self is senior designer with a highend audio manufacturer, as well as author of numerous magazine articles in the pages of Electronics World Wireless World. His career in audio design is the foundation of a book that is based solidly on practical experience as well as a dedication to a methodology based on measurement, analysis and scientific design principles. The fourth edition includes new material on DC offset protection circuitry, the design of DC servos and electrical safety and safety standards. In addition, there is a new chapter on Class D power amplifiers.

audio power amplifier design handbook 3rd edition

Share this:. In the McMichael company presented King George It is easy to get sound out of vacuum tube audio circuitry With these pre- amplifier and power amplifier circuits you can scale your design to a complete home

Easy - Download and start reading immediately. Flexible - Read on multiple operating systems and devices. Easily read eBooks on smart phones, computers, or any eBook readers, including Kindle. We cannot process tax exempt orders online. If you wish to place a tax exempt order please contact us.

All rights reserved. Filterless High Efficiency 2. Operat- 8 speaker ing on a single 5V supply, it is capable of driving a 4 speaker load at a continuous average output of 2. Its flexible power supply requirements allow op- eration from 2. Features The gain of the LM is externally configurable which al- lows independent gain control from multiple sources by sum- No output filter required for inductive loads ming the signals.

Published by Foulsham in Slough. Written in English. This book is the essential reference for audio power amplifier designers and engineers. Author Douglas Self covers all the issues of distortion and linearity, power supplies, protection, reliability and layout.