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AMPLIFY
Amplify means to increase or make larger. In the world of
wireless, it generally refers to amplifying a weak signal in a receive
to make it large enough to be able to decode or understand it properly.
Of course amplifiers are also used for audio products to amplify weak
audio signals till they are strong enough such that we can hear them in
either headphones or loudspeakers.
| An amplifier nowadays is mostly a transistor and associated circuitry
that will have two inputs - (1) the signal to be amplified and (2) a
voltage source such as a battery or ac voltage from
a wall plug. The transistor stage and its circuitry uses the
battery power or power from an ac source in order to increase the power
of the incoming signal in voltage level and hence power level also.
(voltage and current are the two elements of electronic power).
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To understand how this works, recall that early vacuum tubes - which
transistors are similar to - were at one time called "valves".
Valves would be a very appropriate name, since it does give a clue how
it works. Consider that the amplifying transistor uses a battery
for power, and that there is a lot of available current on its output.
Think of it now as a pipe on its output that this current will flow
through. But the transistor also has a "valve" - called an emitter
- but let us call it a valve here. The incoming signal does not go
directly to the output. Instead it controls the valve. So a
little bit of power controls the valve and as it does, it allows a great
deal of current to flow in the output "pipe". Since the current
flows in the pipe at the same rate that the valve is being changed, the
two are identical - except that the output is much stronger. The
output "pipe" of a transistor is actually a wired circuit connecting its
"collector" and its "base" where the current will flow. Now if
this one transistor stage does not amplify enough, the number of
transistor stages can be repeated until the current, voltage and hence
power are what is needed. This is called amplification.
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