Practical Electronics and MicroElectronics PDF

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mainly they have been designed for

maximum power and minimum dis-
tortion, resulting in modules that will

only fit one or two per case (unless you
use a huge case!).
We have published amplifier designs
using all-in-one IC ‘chip’ amps like the

LM1875T. They are always quite com-
promised, both in terms of maximum

power output (typically topping out
at around 30-40W) and performance,
with distortion and noise figures far
worse than a discrete amplifier.
This design offers an excellent
compromise between the two. It’s
cheaper and easier to build than
our best Hi-Fi amplifiers while still
delivering plenty of power with very
good performance. And because it’s

so compact and has modest power
supply requirements, you can quite
easily jam half a dozen (or more!) of
them into a reasonably sized chassis.
We designed these for driving
multi-way loudspeaker systems using

an active crossover to split the sig-
nals into frequency ranges to suit

each driver. This approach needs one
amplifier per driver (woofer, tweeter
and so on) but you generally don’t
need as much power per amplifier,
since they are working together.
Initially, we looked at using small,
low-cost Class-D amplifier modules
which could deliver 30-50W.

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quite a bit of searching, we concluded

that there was nothing readily avail-
able with distortion performance

within an order of magnitude of what
we’d call ‘Hi-Fi’. Many smaller Class-D

amplifiers exhibit high-frequency dis-
tortion above 0.5%, worse than many

decent loudspeaker drivers!

In the end, we looked at larger
high-quality amplifiers and shrunk the

design. The result is the Humming-
bird Amplifier Module, which packs

a surprising punch for its size, while
keeping many of the low-distortion
characteristics of the larger amplifiers
from which it takes inspiration. It can
achieve up to 60W into 8W or 100W
into 4W with distortion below 0.0008%
at 1kHz and less than 0.008% all the
way up to 20kHz. That’s way better
than ‘CD quality’.

If you are familiar with larger ampli-
fier topology, then an examination of

the circuit diagram (Fig.7) will show

many similarities between the Hum-
mingbird and larger siblings. On the

other hand, for compactness, the prin-
cipal differences are:

n We opted for one pair of output tran-
sistors, rather than two

Features eatures
● Low distortion and noise
● Extremely compact PCB
● Fits vertically on a 75mm heatsink and can be stacked in a 2RU case
● Produces specified power output continuously with passive cooling
● All through-hole parts
● Low in cost, simple to build
● Onboard DC fuses
● Output over-current and short-circuit protection
● Clean overload recovery with low ringing
● Clean square wave response with minimal ringing
● Tolerant of hum and EMI fields
● Quiescent current adjustment with temperature compensation

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Specifications pecifications
● Output power (±32V rails): 100W RMS into 4W, 60W RMS into 8W
● Frequency response (−3dB): 1Hz to 150kHz
● Signal-to-noise ratio: 118dB with respect to 50W into 4W
● Input sensitivity: 1.2V RMS for 60W into 8W; 1.04V RMS for 100W into 4W
● Input impedance: 22kW || 1nF
● Total Harmonic Distortion (8W, ±32V): <0.008%, 20Hz-20kHz,
50kHz bandwidth 32W (see Fig.2 and Fig.6)
● Stability: unconditionally stable with any nominal speaker load ≥4W
● Power supply: ±20-40V DC, ideally ±34V DC from a 25-0-25 transformer
● Quiescent current: 53mA nominal
● Quiescent power: 4W nominal
● Output offset: typically <20mV (measured)

Details about the Ebook

Title: Practical Electronics and MicroElectronic pdf 

Language: English

Size: 17 MB

Pages: 76

Format: PDF

Category: Electronics Engineering

>>>Click Here to Download the PDF for free<<<

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