Introduction to the working mode and function of amplifiers

Amplifiers are composed of electrical components such as electronic tubes or transistors, power transformers, etc., which can amplify the voltage or power of input signals. Used for communication, broadcasting, radar, television, automatic control and other equipment. The key component in solving signals in automatic control tools is a device that increases the signal range or power. In order to help everyone have a comprehensive understanding, this article will summarize the basic knowledge of amplifiers. If you are interested in the content to be covered in this article, please continue reading.

Amplifier Principle: A phase-locked amplifier is actually an analog Fourier transform. Compared to the signal amplitude value at a specific frequency (parameter input frequency) in the input signal, the output of the phase-locked amplifier is a DC voltage. Other frequency components in the input signal will not be able to make any contribution to the output voltage.

Two sinusoidal signals have a frequency of 1Hz and a phase difference of 90 degrees. The product of the multiplier results in a DC bias sine signal.

If it is the product of 1Hz and 1.1Hz signals, the result of the multiplier product is a modulated signal with a sinusoidal profile and a DC bias of 0.

Only signals that are completely consistent with the reference signal frequency can obtain DC bias at the output end of the multiplier, while other signals are AC signals at the output end. If a low flux filter is added to the output of the multiplier, all the weight of the AC signal is filtered out, and the remaining DC weight is only proportional to the range of signal weight at a specific frequency in the input signal.

Principle of amplifier function: High frequency power amplifier is used at the end of the transmitter. Its function is to amplify the power of the high-frequency modulated signal to meet the requirements of the push power, and then radiate it into space through the antenna to ensure that the receiver receives a satisfactory signal level within a certain area, without affecting the communication of adjacent channels.

High frequency power amplifier is a key component of the push device in communication systems. According to the width of its operating frequency band, it is divided into narrowband high-frequency power amplifiers and broadband high-frequency power amplifiers. Narrowband high-frequency power amplifiers generally use a frequency selection circuit with filtering effect as the output circuit, also known as a tuned power amplifier or resonant power amplifier; The output circuit of a broadband high-frequency power amplifier is a transmission line transformer or other broadband pairing circuit, also known as an untuned power amplifier. High frequency power amplifier is an energy converter that converts the direct current heat transfer provided by the power supply into high-frequency AC output. It is known in the course of "Low frequency electronic circuits", and the amplifier can be divided into three operating states: A, B, and C based on the difference in current conduction angle. Class A amplifier has a current flow angle of 360o, suitable for small signal low-power amplification. The flow angle of Class B amplifier current is equal to 180o; The flow angle of Class C amplifier current is less than 180o. Both Class B and Class C are suitable for high-power operation. The output power and efficiency of Class C operating state are the highest among the three operating states. Most high-frequency power amplifiers operate in Class C. However, the current waveform distortion of Class C amplifiers is too large, so they cannot be used for low-frequency power amplification, and can only be used for resonant power amplification of tuned circuits as loads. Due to the filtering ability of the tuning circuit, the circuit current and voltage still tend to sinusoidal waveforms, resulting in very small frame loss.

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