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Amplifiers Sound System

Amplifiers sound system

The active devices used in the amplifiers are mainly transistors (bipolar or field-effect transistors). Electrons (including high-power emission tubes) are also used in applications where the operating frequency is high or the output power is required. tube. (A), A (B), B (B), C (C) and D (D) are the same as those of the active device. The table shows the highest efficiency of the sine wave with different types of power amplifiers.

Power amplifier often used in broadcasting, communication transmitter output stage, the sound system output stage and control system drive actuator amplifier. Different applications, performance requirements are different, the composition of the circuit and the type of work is also different. Commonly used linear amplifier, resonant amplifier, broadband amplifier circuit. To improve the output power, power synthesis technology can be used.

Linear amplifiers are used for applications requiring non-linear distortion. Common circuit in the form of single-tube amplifier circuit and push-pull amplifier circuit. Single-tube amplifier circuit circuit and voltage amplifier similar to the type of work must be, the lowest efficiency, and more for low-power amplifier. Push-pull amplifier circuit consists of two active devices, respectively, with a phase difference of 180 ° input signal excitation, and then their output signal inversion superimposed on the load. Figure 1 shows the use of transformers to achieve reverse stack push-pull amplifier principle circuit. This circuit theoretically two devices can work in class B, and the output is not distorted. But the actual active device characteristics are not entirely ideal and need to work in class B. The push-pull amplifier circuit can also be composed of pairs of polarized transistors that are complementary to pairs of CPNP and NPN bipolar transistor pairs or N-channel and P-channel. The use of their complementary characteristics of the circuit, no phase difference of 180 ° of the two input signals, the output signal does not need to reverse the superposition. This circuit can be all composed of transistors and resistors, easy to integrate, and more for integrated power amplifier.

Resonance amplifier to resonant circuit as the active device load, specifically to amplify the narrow band signal amplifier. This amplifier allows the current waveform is very distorted, and then use the resonant circuit to filter out the harmonic; can make the active device in the C class, in order to obtain high efficiency; used for high-power transmitter in the final stage. If the resonant circuit is tuned to the harmonics of the input signal and the appropriate operating point is selected, the frequency multiplier can be constructed.

Broadband amplifier with transmission line transformer as the load of active devices. The upper limit of this amplifier can reach hundreds of megahertz, wide band coverage. Transmission line transformer in accordance with the transmission line and the composition of the working principle of the transformer.