What architectures of power amplifiers are used in various industries?

[Kfactor]

Hi,

What class of power amplifier or what architecture of power amplifier are used in various industries (i.e. wireless, telecom, cable, audio etc.) ?

Which is most popular or efficeint or linear ?

Please shed some light if you can .............

thanks,

 

[seadolphine2000]

uses of class b power amplifier in industry

Amplifiers used in audio systems are class B
(Pull-Push) amplifiers.

 

[Kral]

application class b power amplifier in industry

Kfactor,
Class A
. Least efficient, lowest distortion, used in audio and other applications
. that require high linearity.
Class B
. More efficient than claas A, used in audio, and RF applications
. that require a (relatively) linear amplifier, such as single
. sideband RF power.
Class C
. More efficient than class B, but non-linear. Used in RF power applications. The
. class C amplifier is essentially a synchronous switch that operates at a
. frequency that is identical to the frequency of the output resonant "tank"
. (a parallel resonant L-C circuit).
Class G
. This is a class, used mostly in audio, in which the power supply
. voltage is varied according to the output power required. The output
. stage is almost always class B, although there is no reason that it
. could not be class A.
Class D
. This is the most efficient. It is a switching output sstage that uses PWM
. (Pulse width modulation), usually followed by a low pass filter to remove the
. carrier frequency. This is very popular in powered subwoofer amplifiers,
. because of the high power required to drive the low-efficiency sub-woofers.
Regards,
Kral

 

[newcpu]

high power amplifier class g

Class E power amplifier is used in transceiver for communications.

 

[Kfactor]

high power transistor output audio amplifier

What's the difference between class D and class E ?

 

[sunking]

class h power amplifier

All of these terms refer to the operating characteristics
of the output stages of amplifiers.

Briefly, Class A amps sound the best, cost the most, and are the
least practical. They waste power and return very clean signals.
Class AB amps dominate the market and rival the best Class A
amps in sound quality. They use less power than Class A, and
can be cheaper, smaller, cooler, and lighter. Class D amps are
even smaller than Class AB amps and more efficient, because
| they use high-speed switching rather than linear control.
| Starting in the late 1990s, Class D amps have become quite
| good, and in some cases rivaling high quality amps in sound
| quality. Class B & Class C amps aren't used in audio.

In the following discussion, we will assume transistor output
stages, with one transistor per function. In some amplifiers,
the output devices are tubes. Most amps use more than one
transistor or tube per function in the output stage to increase
the power.

Class A refers to an output stage with bias current greater
than the maximum output current, so that all output transistors
are always conducting current. The biggest advantage of Class A
is that it is most linear, ie: has the lowest distortion.

The biggest disadvantage of Class A is that it is inefficient,
ie: it takes a very large Class A amplifier to deliver 50
watts, and that amplifier uses lots of electricity and gets
very hot.

Some high-end amplifiers are Class A, but true Class A only
accounts for perhaps 10% of the small high-end market and none
of the middle or lower-end market.

Class B amps have output stages which have zero idle bias
current. Typically, a Class B audio amplifier has zero bias
current in a very small part of the power cycle, to avoid
nonlinearities. Class B amplifiers have a significant advantage
over Class A in efficiency because they use almost no
electricity with small signals.

Class B amplifiers have a major disadvantage: very audible
distortion with small signals. This distortion can be so bad
that it is objectionable even with large signals. This
distortion is called crossover distortion, because it occurs at
the point when the output stage crosses between sourcing and
sinking current. There are almost no Class B amplifiers on the
market today.

Class C amplifiers are similar to Class B in that the output
stage has zero idle bias current. However, Class C amplifiers
have a region of zero idle current which is more than 50% of
the total supply voltage. The disadvantages of Class B
amplifiers are even more evident in Class C amplifiers, so
Class C is likewise not practical for audio amps.

Class A amplifiers often consist of a driven transistor
connected from output to positive power supply and a constant
current transistor connected from output to negative power
supply. The signal to the driven transistor modulates the
output voltage and the output current. With no input signal,
the constant bias current flows directly from the positive
supply to the negative supply, resulting in no output current,
yet lots of power consumed. More sophisticated Class A amps
have both transistors driven (in a push-pull fashion).

Class B amplifiers consist of a driven transistor connected
from output to positive power supply and another driven
transistor connected from output to negative power supply. The
signal drives one transistor on while the other is off, so in a
Class B amp, no power is wasted going from the positive supply
straight to the negative supply.

Class AB amplifiers are almost the same as Class B amplifiers
in that they have two driven transistors. However, Class AB
amplifiers differ from Class B amplifiers in that they have a
small idle current flowing from positive supply to negative
supply even when there is no input signal. This idle current
slightly increases power consumption, but does not increase it
anywhere near as much as Class A. This idle current also
corrects almost all of the nonlinearity associated with
crossover distortion. These amplifiers are called Class AB
rather than Class A because with large signals, they behave
like Class B amplifiers, but with small signals, they behave
like Class A amplifiers. Most amplifiers on the market are
Class AB.

Some good amplifiers today use variations on the above themes.
For example, some "Class A" amplifiers have both transistors
driven, yet also have both transistors always on. A specific
example of this kind of amplifier is the "Stasis" (TM)
amplifier topology promoted by Threshold, and used in a few
different high-end amplifiers. Stasis (TM) amplifiers are
indeed Class A, but are not the same as a classic Class A
amplifier.

Class D amplifiers use switching techniques to achieve even
higher efficiency than Class B amplifiers. As Class B
amplifiers used linear regulating transistors to modulate
output current and voltage, they could never be more efficient
than 71%. Class D amplifiers use transistors that are either on
or off, and almost never in-between, so they waste the least
amount of power.

Obviously, then, Class D amplifiers are more efficient than
Class A, Class AB, or Class B. Some Class D amplifiers have
>80% efficiency at full power. Class D amplifiers can also have
low distortion, although theoretically not as good as Class AB
or Class A.

To make a very good full-range Class D amplifier, the switching
frequency must be well above 40kHz. Also, the amplifier must be
followed by a very good low-pass filter that will remove all of
the switching noise without causing power loss, phase-shift, or
distortion. Unfortunately, high switching frequency also means
significant switching power dissipation. It also means that the
chances of radiated noise (which might get into a tuner or
| phono cartridge) is much higher. If the switching frequency is
| high enough, then less filtering is required. As technology
| improves, industry is be able to make higher switching
| frequency amplifiers which require less low-pass filtering.
| Eventually, Class D amplifier quality could catch up with Class
| A amplifiers. Some believe that it already has.

Some people refer to Class E, G, and H. These are not as well
standardized as class A and B. However, Class E refers to an
amplifier with pulsed inputs and a tuned circuit output. This
is commonly used in radio transmitters where the output is at
a single or narrow band of frequencies. Class E is not used
for audio.

Class G refers to "rail switched" amplifiers which have two
different power supply voltages. The supply to the amplifier
is connected to the lower voltage for soft signals and the
higher voltage for loud signals. This gives more efficiency
without requiring switching output stages, so can sound better
than Class D amplifiers.

Class H refers to using a Class D or switching power supply
to drive the rails of a class AB or class A amplifier, so that
the amplifier has excellent efficiency yet has the sound of a
good class AB amplifier. Class H is very common in professional
audio power amplifiers.