Views: 0 Author: Site Editor Publish Time: 2022-02-28 Origin: Site
How much do you know about car amplifier?
The car power amplifier (Power Amplifier) is the car power amplifier, which is used to amplify the power of the car audio. Its task is to amplify the weak electrical signal from the source to drive the speaker to make sound. To achieve the ideal vehicle effect. The power amplifier circuit consists of a pre-voltage amplifier stage, a booster stage, a power amplifier stage, a speaker, etc. The pre-stage is a voltage amplifier stage. The last stage is the power amplifier stage, which amplifies the power of the signal sent by the pre-stage to obtain enough power to output to the speaker. The boost stage is to provide the larger input signal source power required by the power output stage.
1 Classification of car amplifiers
1. According to the type of power amplifier tube
1. Tube amplifier; it is a power amplifier using electronic tubes.
2. Stone machine; is a power amplifier using transistors.
2. According to its conductive method
The two transistors in the output stage are always in a conductive state, and they keep conducting current regardless of whether there is a signal input, and make these two currents equal to the peak value of the alternating current. At this time, the alternating current flows into the load under the condition of maximum signal. When there is no signal, the two transistors each flow the same amount of current, so there is no unbalanced current or voltage at the output center point, so no current is input to the speaker. When the signal goes positive, the output transistor on the top of the line allows more current to flow, while the output transistor on the bottom reduces the current relatively. Since the current begins to be unbalanced, it flows into the speaker and pushes the speaker to sound.
The working mode of class A power amplifier has the best linearity. Each output transistor amplifies the full wave of the signal, and there is no crossover distortion at all. Even if negative feedback is not applied, its open-loop distortion is still very low, so it is called a The most ideal amplifier circuit design for sound. However, this design has advantages and disadvantages. The biggest disadvantage of class A power amplifiers is low efficiency, because there is still full current flowing in when there is no signal, and all the electrical energy is converted into high heat. When the signal level increases, some power can enter the load, but a lot is still converted to heat.
Class A amplifiers are ideal for replaying music, providing a very smooth sound quality with a round and warm tone and transparent highs that more than compensate for its shortcomings. Class A power amplifiers generate astonishing amounts of heat. In order to effectively deal with heat dissipation, class A power amplifiers must use large heat sinks. Because of its low efficiency, the power supply must be able to provide sufficient current.
A 25W class A power amplifier power supply is capable of at least 100W class AB power amplifier. Therefore, the volume and weight of the A-type machine are larger than that of the AB-type machine, which increases the manufacturing cost and the price is more expensive. In general, Class A amplifiers sell for twice or more than equivalent Class AB amplifiers.
The way it works is that when there is no signal input, no power is consumed because the transistor does not conduct electricity. When there is a signal, each pair of output tubes amplifies half of the waveform, and turns on and off each other to complete a full-wave amplification. When the two output transistors work alternately, crossover distortion occurs, thus forming nonlinearity. Pure class B amps are rare because the distortion is severe at very low signal levels, so crossover distortion makes the sound harsh. Allows the use of smaller heat sinks.
3. Class AB amplifier
Compared with the first two types of power amplifiers, class AB power amplifiers can be said to be a compromise in performance. Class AB amplifiers usually have two bias voltages and also have a small amount of current flowing through the output transistors when there is no signal. It uses Class A working mode when the signal is small to obtain the best linearity. When the signal increases to a certain level, it automatically switches to Class B working mode to obtain higher efficiency.
An ordinary 10-watt Class AB power amplifier works with Class A within 5 watts. Since the power required for listening to music is only a few watts, the Class AB power amplifier uses the Class A power amplifier working mode most of the time, only when music appears. It is converted to class B only when the transient strong sound occurs. This design can achieve excellent sound quality and improve efficiency and reduce heat, it is a quite logical design. Some class AB power amplifiers will set the bias current very high, so that they work in class A in a wider power range, making the sound close to pure class A machine, but the heat generated is relatively increased.
It is only suitable for communication use as it is a very high distortion amplifier.
The transistor it amplifies directly connects its load to the power supply as soon as it is turned on, current flows but the transistor has no voltage, so there is no power consumption. When the output transistor is turned off, the full power supply voltage is present on the transistor, but there is no current and therefore no power consumption, so the theoretical efficiency is 100%.
The advantages of class D amplifier amplification are the highest efficiency, the power supply can be reduced, and almost no heat is generated, so there is no need for a large radiator, the body volume and weight are significantly reduced, theoretically low distortion, and good linearity. However, the work of this kind of power amplifier is complicated, and the added circuit itself is inevitably biased, so there are very few truly successful products, and the price is not cheap.
Written by : Davecl Audio
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