Amplifiers
The practical benefit of active devices
is their amplifying ability. Whether the device in question be
voltage-controlled or current-controlled, the amount of power required
of the controlling signal is typically far less than the amount of power
available in the controlled current. In other words, an active device
doesn't just allow electricity to control electricity; it allows a
small amount of electricity to control a large amount of
electricity.
Because of this disparity between
controlling and controlled powers, active devices may be
employed to govern a large amount of power (controlled) by the
application of a small amount of power (controlling). This behavior is
known as amplification.
It is a fundamental rule of physics that
energy can neither be created nor destroyed. Stated formally, this rule
is known as the Law of Conservation of Energy, and no exceptions to it
have been discovered to date. If this Law is true -- and an overwhelming
mass of experimental data suggests that it is -- then it is impossible
to build a device capable of taking a small amount of energy and
magically transforming it into a large amount of energy. All machines,
electric and electronic circuits included, have an upper efficiency
limit of 100 percent. At best, power out equals power in:
Usually, machines fail even to meet this
limit, losing some of their input energy in the form of heat which is
radiated into surrounding space and therefore not part of the output
energy stream.
Many people have attempted, without
success, to design and build machines that output more power than they
take in. Not only would such a perpetual motion machine prove
that the Law of Energy Conservation was not a Law after all, but it
would usher in a technological revolution such as the world has never
seen, for it could power itself in a circular loop and generate excess
power for "free:"
Despite much effort and many unscrupulous
claims of "free energy" or over-unity machines, not one has ever
passed the simple test of powering itself with its own energy output and
generating energy to spare.
There does exist, however, a class of
machines known as amplifiers, which are able to take in
small-power signals and output signals of much greater power. The key to
understanding how amplifiers can exist without violating the Law of
Energy Conservation lies in the behavior of active devices.
Because active devices have the ability
to control a large amount of electrical power with a small amount
of electrical power, they may be arranged in circuit so as to duplicate
the form of the input signal power from a larger amount of power
supplied by an external power source. The result is a device that
appears to magically magnify the power of a small electrical signal
(usually an AC voltage waveform) into an identically-shaped waveform of
larger magnitude. The Law of Energy Conservation is not violated because
the additional power is supplied by an external source, usually a DC
battery or equivalent. The amplifier neither creates nor destroys
energy, but merely reshapes it into the waveform desired:
In other words, the current-controlling
behavior of active devices is employed to shape DC power from the
external power source into the same waveform as the input signal,
producing an output signal of like shape but different (greater) power
magnitude. The transistor or other active device within an amplifier
merely forms a larger copy of the input signal waveform out of
the "raw" DC power provided by a battery or other power source.
Amplifiers, like all machines, are
limited in efficiency to a maximum of 100 percent. Usually, electronic
amplifiers are far less efficient than that, dissipating considerable
amounts of energy in the form of waste heat. Because the efficiency of
an amplifier is always 100 percent or less, one can never be made to
function as a "perpetual motion" device.
The requirement of an external source of
power is common to all types of amplifiers, electrical and
non-electrical. A common example of a non-electrical amplification
system would be power steering in an automobile, amplifying the power of
the driver's arms in turning the steering wheel to move the front wheels
of the car. The source of power necessary for the amplification comes
from the engine. The active device controlling the driver's "input
signal" is a hydraulic valve shuttling fluid power from a pump attached
to the engine to a hydraulic piston assisting wheel motion. If the
engine stops running, the amplification system fails to amplify the
driver's arm power and the car becomes very difficult to turn.
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