Amplifier: the core engine of signal enhancement
Principle
The core of the amplifier is based on the nonlinear characteristics of active devices (such as transistors and operational amplifiers), and the energy of the input signal is converted into a more energetic output signal through external energy (such as DC power supply). Take the transistor amplifier as an example, when a weak signal is input to the base, the current amplification of the transistor makes the collector current more variable, which is converted into voltage amplification through the load resistance. The key is to use the current-voltage control relationship of the device to establish a proportional mapping between input and output, and at the same time suppress distortion through the negative feedback circuit to ensure that the signal waveform is amplified according to the set gain without distortion.
Function
Signal enhancement: Raise weak signals (such as the sound acquired by the microphone and the radio frequency signals received by the antenna) to a level that can drive subsequent circuits. For example, the audio amplifier amplifies the millivolt-level signal to the volt-level to push the speaker. Impedance matching: Build an interface with low output impedance and high input impedance between the signal source and the load to reduce signal attenuation. For example, the RF amplifier matches the antenna and the receiver to improve the efficiency of energy transmission. Signal processing: As the core module of the analogue circuit, it is combined with filters, modulators, etc. to realise signal selection, frequency transformation and other functions, such as amplifying specific frequency band signals in the tuning circuit.
Usage scenarios
Consumer electronics: audio amplifiers in mobile phones and TVs drive speakers, and the amplification circuit in front of the camera image sensor enhances the optical signal. Communication system: the radio frequency amplifier of the base station improves the signal coverage, and the optical amplifier (such as EDFA) in optical fibre communication compensates for the long-distance transmission loss. Industrial control: The sensor signal amplification circuit converts weak physical quantities (temperature, pressure) into measurable voltage, and amplifies bioelectric signals such as electrocardiogram and electroencephalogram in medical equipment. Scientific research field: high-precision equipment such as particle accelerators and radio telescopes rely on low-noise amplifiers to extract weak signals, and amplify stellar radiation signals in astronomical observations to analyse the spectrum. As a bridge between weak signals and practical applications, the amplifier's performance (such as gain bandwidth product and noise coefficient) directly determines the sensitivity and reliability of the system, and is an indispensable basic component in modern electronic technology.
