- Oct 13, 2017 -
An amplifier is a device that amplifies the voltage or power of an input signal, consisting of a tube or transistor, a power transformer, and other electrical components. Used in communications, broadcasting, radar, television, automatic control and other devices.
Principle: The High-frequency power amplifier is used for the final stage of the transmitter, the function is to amplify the high-frequency modulated wave signal to meet the request of transmitting power, then the antenna will radiate it to space to ensure that the receiver in a certain area can receive the satisfactory signal level, and does not disturb the communication of the neighboring channel.
The high frequency power amplifier is an important component of the communication system. Divided into narrowband high-frequency power amplifier and wideband high frequency power amplifier according to its working band width, narrowband high frequency power amplifier is usually used as output circuit for frequency selective filter, so it is called tuned power amplifier or resonant power amplifier. The output circuit of wideband high frequency power amplifier is Transmission line transformers or other broadband matching circuits, therefore, are also known as non tuned power amplifiers. High-frequency power amplifier is a kind of energy conversion device, it converts the DC energy supplied by the supply into high-frequency AC output in the course of "low frequency electronic circuit", the amplifier can be divided into a, B and C working state according to the difference of current conduction angle. The current flow angle of a type amplifier is 360o, which is suitable for small signal low power amplification. The circulation angle of the current of the Class B amplifier is approximately equal to 180o, and the current angle of the C amplifier is less than 180o. Class B and C are suitable for high-power working state of the output power and efficiency of three kinds of working state of the highest. Most high-frequency power amplifiers work in Class C. However, the current waveform of the C-type amplifier is too distorted, so it can not be used in the low-frequency power amplification, and can only be used to amplify the resonant power using the tuning loop as the load. Because the tuning circuit has filtering ability, the circuit current and the voltage are still very close to the sine wave, the distortion is very small.
The amplifier is mainly used to detect weak signal with low signal-to-noise ratio. Even if the useful signal is submerged in the noise signal, even if the noise signal is much larger than the useful signal, you can accurately measure the amplitude of the signal by knowing the frequency value of the useful signal.