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Deep analysis of audio power amplifier

2020-12-04 08:29:07

Power amplifier, referred to as power amplifier, is the audio signal voltage and current comprehensive amplification, in order to get power amplification. The position of the power amplifier in the system diagram is in front of the loudspeaker system. Its output is directly sent to the loudspeaker system to drive the loudspeaker system. Since the output sensitivity of the power amplifier is generally about 0dB, the input signal added to the power amplifier is generally taken from the 0dB output signal of the mixer or peripheral equipment.



For the low-level output signal such as microphone, it must be amplified by preamplifier or voltage amplification by mixer to drive the power amplifier. The output of preamplifier, mixer or peripheral equipment is voltage signal, which can only output very small current, not power signal, so they can not be used to drive the loudspeaker system. The audio signal must be further voltage amplified by power amplifier, and finally the current and power are amplified to make it have enough power output, which is enough to drive the loudspeaker system Make, radiate sound, that is to push the sound box to work normally.


1,Balanced input, unbalanced input socket


2,The function of balanced unbalanced conversion stage is to convert balanced input signal into unbalanced signal.


3,Line output isolation stage is used to isolate the input signal to the power amplifier and then output it to the outside. When a signal needs to drive multiple power amplifiers at the same time, simple parallel mode will reduce the total output impedance. As a result, the actual output signal amplitude of the front-end equipment will be reduced, that is, the actual input signal amplitude of a power amplifier will be reduced. If this mode is adopted, the load impedance without signal will be equivalent to a power amplifier Input impedance.


4,The volume adjustment stage, in fact, takes the required amount from the total input signal through the potentiometer and adds it to the later stage, so that the output power is the required value.


5,The main task of the input stage and the secondary stage is to buffer and provide a certain amount of voltage at the same time. If there is clipping phenomenon in the power amplifier, the wave elimination indication is given so that the operator can reduce the volume appropriately. This set is often in the form of differential amplifier circuit.


6,In the main voltage amplifier stage, this stage provides large voltage amplification factor, and the open-loop voltage amplification factor of the whole power amplifier mainly depends on this stage.


7,Because the main voltage amplification stage can only provide a very small output signal current, the primary stage is to amplify the main voltage and provide a small signal current, and amplify the signal current dozens of times to more than 100 times, while the signal voltage is not increased, but slightly reduced. This stage uses emitter follower circuit, that is, common collector circuit Pole circuit.


8,The driving stage further amplifies the signal current that has been amplified by the pre driving stage, and the amplification factor of the signal current is about tens to 100 times, so as to provide enough signal driving current for the power output stage. Like the pre driving stage, the signal voltage is not amplified, but slightly reduced. This stage also uses emitter follower circuit.


9,The power output stage will amplify the signal current again. Like the pre push stage and push stage, the signal voltage is not amplified, but slightly reduced. This stage also uses emitter follower circuit. This stage is the last output stage of the whole power amplifier channel. Its output voltage depends on the driving signal voltage added to this stage, while the output current is the main output stage It depends on the ratio of the output signal voltage to the load impedance, which means that the output current cannot increase infinitely with the infinite decrease of the load impedance. If it exceeds the product of the current amplification factor of the current level and the driving signal current added to the current level, the current level will not be able to provide, and the output signal current is also affected by the output power of the DC working power supply provided for the current level In fact, the main limitation of the current is the parameter limitation of the output power transistor, so when using the power amplifier, we must pay attention not to overload the power amplifier, otherwise it may exceed the capacity of the output power transistor and damage the power amplifier.



Through the above introduction, do you have a new understanding of audio amplifier? Xiao Bian reminds you to love the sound while enjoying the hearing enjoyment it brings.


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