Q. What is meant by amplification?

The basic amplifying elements are, namely valves (vacuum tubes), bipolar transistors and FETs. The term "amplify" basically means to make stronger. The strength of a signal (in terms of voltage) is referred to as amplitude, but there is no equivalent for current.

To understand how any amplifier works, you need to understand the two major types of amplification, and a third "derived" type:

· Voltage Amplifier - an amp that boosts the voltage of an input signal

· Current Amplifier - an amp that boosts the current of a signal

· Power Amplifier - the combination of the above two amplifiers

In the case of a voltage amplifier, a small input voltage will be increased, so that for example a 10mV (0.01V) input signal might be amplified so that the output is 1 Volt. This represents a "gain" of 100 - the output voltage is 100 times as great as the input voltage. This is called the voltage gain of the amplifier.

In the case of a current amplifier, an input current of 10mA (0.01A) might be amplified to give an output of 1A. Again, this is a gain of 100, and is the current gain of the amplifier. If we now combine the two amplifiers, then calculate the input power and the output power, we will measure the power gain:

P = V x I (where I = current, note that the symbol changes in a formula)