Three working states of power amplifier tube

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Three working states of power amplifier tube [Copy link]

Three working states of power amplifier tube

The low-frequency power output stage is divided into three types: Class A, Class B, and Class C according to the working status of the power amplifier tube.

They each have their own characteristics:

(1) The main advantage of Class A power output stage is low distortion, and the main disadvantage is low efficiency.

Its output power Po, power consumption PD, collector maximum power consumption Pcmax and efficiency are:

P _o =E _c ² /2R _L P _D =2E _c ² /R _L

P _cmax =2E _c ² /R _L =4P _o η= P _o / P _D =1/4=25%

(2) The main advantage of the Class B power output stage is its high efficiency, and its main disadvantage is the existence of severe crossover distortion.

Its output power Po, power consumption PD, collector maximum power consumption Pcmax and efficiency are:

P _o =E _c ² /2R _L P _D =2E _c ² / π R _L

P _cmax =2E _c ² / π ² R _{L ?} 0.4P _o η= P _o / P _D = π /4=78%

(3) Class A and B power output stages absorb the advantages of Class A and Class B, and are therefore widely used.

But its circuit structure is more complicated than Class A and Class B. As shown in the figure below:

(a) Using a diode to provide bias voltage (b) Using a triode constant voltage source to provide bias

Class AB complementary power amplifier circuit

陈傲然

Thanks for sharing!

gmchen

Class C amplifiers are mainly used for high-frequency amplifiers. High efficiency is its advantage, but it usually requires an LC circuit to select the required frequency, so it is not suitable for low-frequency circuits.

gmchen

In fact, there are also Class D, Class E, Class F and other power amplifier circuits. These power amplifiers are also high-frequency amplifiers, but Class D can be used for low-frequency amplification, and its efficiency is much higher than Class B and Class AB, and far higher than Class A.