Products >> Analog signal chain chip >> Amplifier/comparator

Amplifier is an electronic device or circuit that can increase the amplitude of an input signal. It can amplify weak electrical signals (such as the tiny signals output by sensors) so that the signal strength is sufficient for subsequent electronic devices (such as analog - to - digital converters, controllers, etc.) to process effectively. For example, in an audio system, the weak audio signal produced by a microphone needs to be amplified by an amplifier before it can drive a speaker to produce a loud enough sound.
Working Principle
- It is mainly based on the amplification characteristics of transistors (such as bipolar junction transistors (BJT) or field - effect transistors (FET)). Taking BJT as an example, a small change in the voltage between the base and the emitter will cause a relatively large change in the collector current, thus realizing signal amplification. In an actual amplifier circuit, a bias circuit is reasonably set to ensure that the transistor works in an appropriate amplification region, and a feedback circuit is used to stabilize the amplification factor and improve the signal quality.
Main Types
- Operational Amplifier (Op - Amp)
  - It is a high - gain, direct - coupled amplifier with two input terminals (non - inverting input terminal and inverting input terminal) and one output terminal. The operational amplifier can implement a variety of mathematical operations, such as addition, subtraction, integration, and differentiation. It is widely used in signal processing, instrumentation, and control systems. For example, in an audio mixing circuit, an operational amplifier can be used to add multiple audio signals in a certain proportion.
- Power Amplifier
  - It is mainly used to provide sufficient power signals to the load. In an audio power amplifier, it can amplify the signal output by the pre - amplifier to drive a low - impedance speaker. Power amplifiers can be divided into class A, class B, class AB, and class D according to the working mode. Different types have their own characteristics in terms of efficiency and distortion.
- Instrumentation Amplifier
  - It is specially designed to amplify weak differential signals and has the characteristics of high - input impedance and high - common - mode - rejection - ratio. It is often used in situations where weak signals need to be accurately measured, such as the measurement of bio - electrical signals (electrocardiogram, electroencephalogram, etc.) and the amplification of sensor signals in industrial process control.
Main Characteristics
- Gain
  - It refers to the ratio of the amplitude of the output signal to the input signal and is an important indicator to measure the amplification ability of the amplifier. For example, for an amplifier with a gain of 100, when the amplitude of the input signal is 1mV, the amplitude of the output signal will be 100mV.
- Bandwidth
  - It represents the frequency range in which the amplifier can effectively amplify the signal. For high - frequency signal amplification, an amplifier with sufficient bandwidth is required, otherwise signal distortion will occur.
- Linearity
  - It describes the degree of linear relationship between the output signal and the input signal of the amplifier. Good linearity can ensure that the signal does not produce serious distortion during the amplification process