There was a valuable learning opportunity in front of me I do not cherish, lost only a rude awakening after know, God can not give me a chance, so I can only again Tucao own brain-dead tears again reviewed, there is no regret medicine may eat, only it is not too late to remedy the situation
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First, first thoroughly understand what is PA?
Description amplified power is not a voltage rather than current, right?
How it works: by the action of the current control transistor to the switching power supply in accordance with the current input signal changes, using the amplification transistor, the collector current is always amplifying the base current, the current amplification can be obtained and then subjected to constant current and voltage amplification, the power amplification is completed.
Can stranded input power into AC output power
Transistors operate at high signal operating conditions, the operating point will be greatly swung up and down. Once the operating point of the linear region out of the input or output, nonlinear distortion occurs.
Voltage amplification circuit to obtain undistorted load voltage signal, the number of main indicators Taryn is the voltage gain, input and output impedance and so on, but power output is not necessarily large. It is not the same amplifier, power amplifier required to obtain a certain undistorted output power, used to work under large signal state, so output power, higher efficiency, nonlinear distortion is smaller. Another serious problem is the heat.
Second, the principle is what does?
First we have to define a basic principle: to NPN transistor as an example: When we work to ensure that the emitter junction is forward biased, that this time the base voltage level (P) is positive, then PN junction barrier reduced, which when the dominant diffusion current, electrons from the P region into the N region, and also to ensure that the collector junction reverse biased, then the barrier height increases under the action of an electric field, the minority carrier electrons from the P base region is stage N into the collector region.
What is the quiescent operating point: that is the intersection of the linear part and nonlinear part
DC linear portion curves UCE characteristic IV curve and IC, the transistor is non-linear portion of the characteristic curve of the output
Quiescent operating point must be the intersection of DC and AC load line load line.
Click the static work is too low, will lead to cut-off distortion, on the contrary, it will produce saturation distortion.
Third, what kind of distortion?
What are the various distortions like?
Fourth, what is the DC and AC load line load line?
Fifth, what is a Class A amplifier circuit:
Group A zoom: operating point is selected in the output characteristic curve of the intermediate position signal may be the entire cycle: throughout the cycle of the input signal has a current flows through the amplifier member, such distortion but low efficacy.
Sixth, what is the push-pull circuit B:
Seventh, what is OTL circuit:
OTL is a push-pull amplifier circuit output transformer power. Typically a single power supply, the output from the midpoint of the two series by capacitive coupling the output signal. Eliminating the need for the power amplifier circuit output transformer is commonly referred to OTL (Output TransformerLess) circuit.
OTL (Output transformerless) circuit without an output transformer of the power amplifier circuit. Past to use more powerful amplifier coupling transformer, impedance transformation in order to solve the problem, a circuit to the optimum load value.
Eighth, what is OCL circuit?
OCL (Output CapacitorLess) is OTL circuit upgrade, eliminating the need for the output terminal means a large capacity power amplifier circuit , the output capacitor is omitted, so that the low frequency response of the system smoother. Disadvantage is that a dual power supply , increases the complexity of the power supply.
Ninth, what is the BTL circuit;
I know a little problem with this picture, in fact, look at the power on the line, left voltage is positive when the right is negative, the left is negative when the right is positive, while the tube 12 is the same pipe NPN 34 is another tube PNP so that is in the conducting state alternately.
This time should be recognized that the meaning of a push-pull alternately turned on
Tenth, what is the crossover distortion?
Class A amplifiers also known as Class A
Class B, also known as B
Also known as AB class A and B category
丁类功放（D类）：利用极高频率的转换开关电路来放大音频信号。 特点：具有效率高，体积小的优点。许多功率高达1000W的丁类放大器，体积只不过像VHS录像带那么大。这类放大器不适宜于用作宽频带的放大器，但在有源超低音音箱中有较多的应用。
以下来自摘抄：
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作者：佛系-楠
来源：CSDN
原文：https://blog.csdn.net/qq_21990661/article/details/81040993
版权声明：本文为博主原创文章，转载请附上博文链接！
甲类工作状态：整个工作周期内晶体管的集电极电流始终是流通的，放大器的效率最低，带来的是非线性失真度比较小。一般用于对失真比较敏感的场合，比如HI-FI音响。
乙类工作状态：半个周期工作另半个周期截止，乙类工作状态也称为B类工作状态。两只互补的晶体管推挽工作，效率比甲类功放高，但存在交越失真的问题，一般功率放大器采用这种形式。
甲乙类工作状态：它是介于甲类和乙类之间的工作状态，即晶体管工作周期大于一半，这种功放的特性介于甲类和乙类。
丙类工作状态：这种状态下，晶体管工作的时间小于半个周期，丙类工作状态又称为C类工作状态，丙类功放一般用于高频的谐振功放。
丁类工作状态：把声音信号调制为PWM形式，晶体管工作在开关状态，输出端通过LC滤波器恢复信号波形。效率高，高频特性差，用于小型化电池供电以及要求高效率的场合。
