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Brian Burk

Dec 22, 2015

Mid/High-Power
Class D Amplifiers

TPA3251D2

audio
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Related

Setting the new standard: High-definition audio is changing the
way we listen

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High-definition audio is becoming easier to access through a number of new
devices and services that offer the highest-quality sound and content. You have
likely heard of the ongoing wireless high-fidelity audio craze (hi-fi, Wi-Fi),
with consumers demanding high-quality audio that they can stream over Wi-Fi from
any room in their home. You may have also seen that new streaming services offer
CD-quality or better audio content that just wasn’t available before. It is
clear that the popularity of the CD is quickly becoming a thing of the past, and
it’s time to deliver higher-quality sound that both the casual listener and
audiophile demand.

This is the first post in a four-part blog series where I’ll discuss the
demands of delivering high-quality audio in relevant form factors, I'll examine
what high quality audio is and also how to address it.

High-quality or high-definition audio is more than just music enjoyed by
Golden-Ear audiophiles; it is a way for everyone to have a more immersive
experience. With high-quality audio, you will feel as if you are in the same
room or venue as a musician, or watching a movie in a different world.

Here are key parameters that make the biggest impact when designing
high-quality audio systems.

Output power – higher output power means louder audio; however, peak
output power for quick audio transients is also important to maintain audio
linearity.

Bandwidth, sample rate, bit rate – higher bandwidth is important to
deliver the smallest details of sound at the highest frequencies. For example,
at a 40kHz sample rate, a 20kHz audio signal will have two samples per cycle.
At a 192kHz sample rate, a 20kHz audio signal will have nine to 10 samples per
cycle. Whether it is in the analog or digital domain, more bandwidth enables
more audio detail.

Total harmonic distortion (THD) – a measurement of distortion that
measures the linearity of an amplifier, but more important the ability to
accurately reproduce an audio recording. The lower the THD, the better the
audio performance.

Noise and signal-to-noise (SNR) ratio – this is the amount of noise or the
ratio of signal to noise that an amplifier can deliver. The lower the amount
of noise, the less “hiss” sound on a speaker.

In addition to audio requirements, there are a few power and form-factor
requirements to consider:

Efficiency or power consumption – the lower the on-chip power dissipation,
the smaller the solution size. Class-D amplifiers offer the highest efficiency
and likewise the smallest size.

Idle power consumption – amplifiers should not only be efficient at
maximum output power, but also at low output power. Audio generally has lower
output power with high peak-power requirements.

Audio source – the audio source is important because it determines the
input audio quality. Which medium is the source coming from? Is the input a
Blu-ray disc, Wi-Fi, Bluetooth® or something else?

I have found that the TPA325xD2 family of high-performance Class-D audio
amplifiers improves the audio performance for hi-fi devices. The TPA3251D2 class-D amplifier has a closed-loop architecture,
which enables higher bandwidth and lower distortion audio than other high-power
Class-D amplifiers. During my own personal listening tests, it sounded
comparable to some of the highest-end audio amplifiers available on the
market.  The table below shows a few of the systems I listened to when I
did my listening test.

Table 1: Performance and Feature
Comparisons

The TPA3251D2
delivers the performance of a Class-A or AB amplifier with the size and
efficiency of a Class-D amplifier, which can benefit end-equipment’s such as
AVR’s, Sound-Bars and Home-Theater-in-a-Box.

Just like the listening tests I did, CES2016 attendees will be able to hear
the difference in sound quality this January. The TPA3251D2 will be featured in the TI Village, located in
rooms N115-N120 at the Las Vegas Convention Center North Hall. Please stop by if
you will be attending CES. For everyone else, check back as I explore the
benefits of recent Class-D amplifier trends, because it is obvious hi-fi audio
is changing the way we listen.

Additional resources

Search TI’s entire mid-/high-power Class-D amplifiers portfolio.

Read the TPA3251D2
data sheet.

Check out the TPA3251D2D2
PurePath™ ultra-HD evaluation module.

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