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Today’s audio amplification technologies need to support portable equipment and audio component designs. While enabling miniaturized devices, they have to maximize the effect of small form factor speakers to generate a big, high quality sound. Excellent EMC performance is a must especially for applications in noisy environments, always ensuring distortion free listening.
|Amplifier Class||Typical Efficiency||Pros||Cons|
|A||~15-35%||No possibility of crossover distortion||Inefficiency = heat
Single-ended designs prone to hum and higher levels of distortion.
|B||~70%||Relatively high efficiency||Potential for significant amounts of crossover distortion and compromised fidelity|
|AB||~50-70%||More efficient than Class-A
|Crossover distortion can be rendered moot.
Efficiency is good, but not great.
|G & H||~50-70%||Improved efficiency over Class-AB||Costlier than Class-AB but higher power levels are achievable in a smaller form factor.|
|D||>90%||Most possible efficiency Light weight||Pulse width modulators operating at relatively low frequencies can compromise high frequency audio reproduction.
Some designs produce varying sound quality depending on speaker load.
Whether it’s home theatre, sound bars or the entertainment system in your vehicle, audio reproduction is being influenced by several trends. More channels are used per unit, more integrated sound processing features, and there is the continual drive towards increased efficiency.
These trends affect the choice of amplifier and how the circuit is designed. Through our deep understanding we have evolved our innovative audio amplification technologies so your systems can meet these increasing needs.
In Class-D architecture, transistors are fully on or off, enabling very low losses and ultra high efficiency (>= 90%). Improving amplifier efficiency also helps designers manage energy consumption, important for applications such as in-car systems, and portable and wearable equipment. Our Class-D technology targets the mid- and high-power segments, from 9 W to 265 W per channel.
The technology offers many more design and performance benefits. ‘Feedback after Filter’ enables cheaper non-linear coils to be used, while the interleaved output stage lowers EMI radiation. Value-added features include increased software flexibility, lower dissipation due to ‘idle power’ modes, and extended diagnostic functionality.
Class-D audio power amplifiers simplify thermal management, thereby trimming size and cost from high-power audio systems. Using an advanced automatic power reduction scheme, our Class-D amplifiers avoid over-temperature conditions resulting in zero audio holes under every condition.
Perhaps one of the most useful properties of Class-AB is the incorporation of a full range of I2C-bus controlled diagnostics, which help increase quality and enable reduced costs. During amplifier start-up, the built-in diagnostics can be used to detect shorted load, open load, short to ground or short to VP. The load condition of all four channels is determined.
Due to low voltage operation, Class-AB amplifiers can support the start-stop capabilities of automotive engines. They can continue operating without audible disturbance during engine start at a battery voltage as low as 6 V – when a voltage drop occurs, the output follows slowly due to an SVR capacitor. Conversely, if the battery voltage rises above 10 V, the DC output voltage relates to the SVR voltage to prevent common mode ripple on the speaker lines.
Furthermore, in best efficiency mode you can achieve low power dissipation.