The purpose of any amplifier to produce the output follows the input signal properties but sufficiently large enough to supply the needs of load connected to it.
We have seen that the amplifier output power is the product of voltage and current (P = VxI) applied to pregnancy, while power input DC voltage and current is the product taken from the power supply.
Although amplifier amplification "class" (where the transistor output 100% time) can be high, the conversion efficiency of DC power supply for AC power production is generally poor in less than 50%. But if we modify "class a" amplifier circuit to work in a "class b" (where each transistor is only 50% of the time) the collector current flows in each transistor 180o only of course. The advantage here is that the DC to AC conversion efficiency is much higher at around 75%, but this configuration "category b" leads to distortion of the signal output that can be unacceptable.
One way to produce an amplifier with high efficiency output to configure "category b" along with low distortion for composition "class" is to create an amplifier circuit that a combination of the previous categories resulted in a new type of amplifier circuit called "class AB amplifier. Then the output stage amplifier class AB amplifier combines the advantages of "class" and "class b" amplifier while minimizing the problems the problems of low efficiency and distortion associated with them.
Class AB amplifier as mentioned above, a combination of categories A and B in this small power outputs as a class a amplifier amplifier but changes a class b amplifier for current outputs is greater. This procedure is achieved by biasing the two transistors in the output stage amplifiers. Then will each transistor between 180o and 360o of time depending on the size of the current and previous production biasing. And then the amplifier output stage acts as a special AB class amplifier.
First, lets look at a comparison between output signals for different classes of amplifier operation.
A comparison between different classes of amplifier
And then you always define categories amplifier as follows:
Category a: single output transistor amplifiers for full 360o turn regulates the input waveform. Category b: two output transistor amplifiers only perform for a half is 180o waveform input. Class AB output transistor action: two speakers somewhere between 180o and 360o of the input waveform. Run the class a
The process class a transistor switch Q point is located near the center of the load line output transistor properties within the region. This allows the transistor action for full 360o output signal varies over the entire cycle of the input signal.
The main advantage of category (a) always exact clone output signal to the input signal distortion reduction. But he suffers from low efficiency, because the transistor bias in the middle of the line load there must always be a suitable domain controller DC current flowing through the transistor switches quiet even if there is no input signal to inflate.
Class b
To run "category b", use transistors switch with two free point (any biasing point) each transistor in the FMCT point. This allows one transistor to amplify the signals across one half of the input waveform, whereas other transistor amplifies the other half. And then integrate these halves inflate together in one production load full waveform cycle. Aka free PNP NPN pair push-pull configuration.
Because an FMCT biasing current zero, quiet when there is no input signal, therefore dissipated any authority or wasted when transistors in quiet situation, increasing the overall efficiency of the amplifier "category b" special "class a"
However, "class b" partial amplifier output so no current flows through both transistors just half a turn following output waveform input, an exact replica of the input signal is distorted waveform output. This distortion occurs in all zero-cross signal input produce what is commonly called the most through distortion as two transistors switch "on".
This problem can be overcome easily defaced by locating the point slightly higher transistor biasing of the FMCT. Of biasing a transistor is slightly higher than the clincher, however without q-the center point of a class A amplifier, we create a class AB amplifier circuit, then the primary purpose of the AB class amplifier to maintain basic configuration "b" at the same time improve the lane
