- Sep 06, 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: High-frequency power amplifier for the transmitter's final stage, the role is to high-frequency modulated signal to power amplification to meet the transmission power requirements, and then through the antenna to radiation to space, to ensure that a certain area of reception The machine can receive a satisfactory signal level and does not interfere with the communication of adjacent channels.
The high frequency power amplifier is an important component of the transmitting device in the communication system. According to the width of its work band is divided into narrowband high-frequency power amplifier and broadband high-frequency power amplifier two, narrowband high-frequency power amplifier is usually selected with frequency filtering circuit as the output circuit, it is also known as tuning power amplifier or Resonant power amplifier; broadband high-frequency power amplifier output circuit is a transmission line transformer or other broadband matching circuit, it is also known as non-tuned power amplifier. The high-frequency power amplifier is an energy conversion device that converts the DC energy of the power supply into a high-frequency AC output. In the "Low-frequency electronic circuit" course, the amplifier can be divided into a different according to the current conduction angle , B, C three types of work. Class A amplifier current flow angle of 360o, suitable for small signal low power amplifier. Class B amplifier current flow angle is about equal to 180o; C class amplifier current flow angle is less than 180o. Class B and Class C are suitable for high power operation. The output power and efficiency of the Class C operating state are the highest of the three operating conditions. Most of the high-frequency power amplifiers work in Class C. However, the current waveform distortion of the Class C amplifier is too large to be used for low frequency power amplification and can only be used to amplify the resonant power using the tuning loop as a load. As the tuning circuit has the filtering ability, the loop current and voltage are still very close to the sine wave, the distortion is very small.
Mainly used to detect the signal to noise ratio is very low weak signal. Even if the useful signal is submerged inside the noise signal, even if the noise signal is much larger than the useful signal, the amplitude of the signal can be accurately measured by knowing the frequency value of the useful signal.