Amplifier Classes

[kasimo420 10+ year member]

Most of you already know but for those who don't here ya go. Message me any questions further then this and I will be happy to answer.

Amplifiers are commonly classified by the conduction angle (sometimes known as 'angle of flow') of the input signal through the amplifying device; see electronic amplifier.

Class A

Where efficiency is not a consideration, most small signal linear amplifiers are designed as Class A, which means that the output devices are always in the conduction region. Class A amplifiers are typically more linear and less complex than other types, but are very inefficient. This type of amplifier is most commonly used in small-signal stages or for low-power applications (such as driving headphones).

Class B

In Class B, there are two output devices (or sets of output devices), each of which conducts alternately for exactly 180 deg (or half cycle) of the input signal.

Class AB

Class AB amplifiers are a compromise between Class A and B, which improves small signal output linearity; conduction angles vary from 180 degrees upwards, selected by the amplifier designer. Usually found in low frequency amplifiers (such as audio and hi-fi) owing to their relatively high efficiency, or other designs where both linearity and efficiency are important (cell phones, cell towers, TV transmitters).

Class C

Popular for high power RF amplifiers, Class C is defined by conduction for less than 180° of the input signal. Linearity is not good, but this is of no significance for single frequency power amplifiers. The signal is restored to near sinusoidal shape by a tuned circuit, and efficiency is much higher than A, AB, or B classes of amplification.

Class D

Class D amplifiers use switching to achieve a very high power efficiency (more than 90% in modern designs). By allowing each output device to be either fully on or off, losses are minimized. A simple approach such as pulse-width modulation is sometimes still used; however, high-performance switching amplifiers use digital techniques, such as sigma-delta modulation, to achieve superior performance. Formerly used only for subwoofers due to their limited bandwidth and relatively high distortion, the evolution of semiconductor devices has made possible the development of high fidelity, full audio range Class D amplifiers, with S/N and distortion levels similar to their linear counterparts.

Other classes

There are several other amplifier classes, although they are mainly variations of the previous classes. For example, Class H and Class I amplifiers are marked by variation of the supply rails (in discrete steps or in 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 frequencies applications where efficiency of the traditional classes 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.

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[kasimo420 10+ year member]

Also, try this website out for alot of good info.

http://www.bcae1.com/ampclass.htm

 

[Rich B 5,000+ posts]

You forgot Class T, which is Tripath's label for amps based on their chipsets.

 

[kasimo420 10+ year member]

Thank you rich b. Was just making a fast post of it. Saw some people had questions about it.

 

[Rich B 5,000+ posts]

Thank you rich b. Was just making a fast post of it. Saw some people had questions about it.

For fast, you're good!

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[azbass 5,000+ posts]

im suprised this was never a sticky.

 

[jmanpc 5,000+ posts]

sticky this motha!

 

[helotaxi 5,000+ posts]

On this forum you're suprised by anything anymore? There are a lot of topics that desrve to be stickys that get f-ed up by the immature loons that troll this forum clogging up the good info with their diarrhea of the keyboard.

kasimo420, thanks, good stuff!

 

[thylantyr 10+ year member]

http://www.zedaudio.com/Technical/Amplifier-Classes.htm

 

[kasimo420 10+ year member]

Yes, please sticky this. Also, anyone who has any other info or links post them up. I think this will help alot of people.

 

[kasimo420 10+ year member]

anyone got any other info ?

 

[djman37 5,000+ posts]

'Class-T' and 'Class-X' are marketing, not classes. For more reading(if it's still up) http://www.tripath.com

 

[PowerNaudio 10+ year member]

http://www.zedaudio.com/Technical/Amplifier-Classes.htm

now that site has the information explaining what the classes are. thats worth of a sticky.

www.tripath.com

that is just a chip amp. plenty of them out there, almost every head unit has one. even cheap *** amplifiers that claim high levels of power have these in them like pyle just to mention one of them.

but there are some chip amps that are actually very good very power full up to 120wrms and are worth every penny. this forum the diyaudio forum has a great deal of info on some of the best chip amps out in the market for the do it your selfers and also how to use them. very interesting site.

if youre into audio electronics.

 

[helotaxi 5,000+ posts]

The Tripath amps weren't "just chip amps." They were chip controlled but the output devices were not on the IC, they were standalone MOSFETs.

 

[PowerNaudio 10+ year member]

The Tripath amps weren't "just chip amps." They were chip controlled but the output devices were not on the IC, they were standalone MOSFETs.

thanks for the info, i didn't read into the site too deep. thats a cool device since it makes for smaller amps and half of the amp is already in a super small package.

i may read deeper into it later. since it seem like it could be use for a cool amplifier project.