Introduction: Power amplifier , as its name suggests, is an instrument that amplifies power . What is the principle of power amplifier ? Please see below for details~~~
First, the power amplifier principle - - What is PA?
Power amplifier, the English name is power amplifier, referred to as power amplifier, commonly known as amplifier. It is an important part of the sound system, which is used to amplify the power of the tiny signal to promote the sound of the sound, and dominate the output sound quality of the entire sound system.
Second, the principle of power amplifier - - working state
The power amplifier has three working states: Class A, Class B, and Class A and B. The specific explanations are as follows:
The working point of the class A power amplifier is located in the middle of the linear region of the output characteristic curve, and the signal current can flow throughout the cycle, which has small distortion, low efficiency and low output power.
The operating point of the class B amplifier is located on the output characteristic curve where the base current is equal to zero. The signal current can only flow in half a cycle, which has large distortion, high efficiency and high output power.
The working point of Class A and Class B power amplifiers is located in the middle of the working point of Class A power amplifier and Class B power amplifier. The signal current flow range is from half cycle to the whole cycle, and its working performance is also between Class A power amplifier and Class B power amplifier. It is an effective combination of Class A power amplifier and Class B power amplifier. It not only solves the efficiency problem of Class A power amplifier, but also solves the distortion problem of Class B power amplifier. It has been widely used.
Third, the principle of power amplifier - - basic composition
The power amplifier is generally composed of a preamplifier, a driver amplifier and a final stage power amplifier. The functions of each component are as follows:
First of all, the preamplifier plays a matching role, with high input impedance and low output impedance, so it can absorb most of the signals from the previous stage, and can also transmit most of the signals to the subsequent stage. At the same time, it is also possible to convert the voltage signal into a current signal and perform an appropriate degree of amplification.
Secondly, the driver amplifier acts as a bridge to further amplify the signal from the preamplifier into a medium power signal and pass it to the final stage power amplifier for better operation.
Finally, the final stage power amplifier plays the most important role, which further amplifies the medium power signal from the driver amplifier into a high-power signal, which drives the speaker to make a sound. The performance of the entire power amplifier is primarily determined by the final stage power amplifier.
Fourth, the principle of power amplifier
The ultimate goal of the power amplifier is to achieve power amplification, using the current control of the triode or the voltage control of the FET.
Taking a triode as an example, since the sound signal is an alternating current signal having different amplitudes and different frequencies, the collector current of the triode is β times the base current, that is, if a small signal current is input at the base of the triode, at the collector. The output current is β times the small signal current, and then the amplified current is isolated by an isolation capacitor to obtain a large signal.
The voltage control of the FET is similar to the current control of the triode, and a large signal is obtained by amplifying the voltage. In the circuit, the power amplification can be achieved by continuous current or voltage amplification.
Power amplifier principle
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