Background a The types of amplifiers can be categorized in different ways. One is by the frequency of the electronic signal being amplified; audio amplifiers amplify signals in the audio(sound)range of less than 20 kHz, RF amplifiers amplify frequencies in the radio frequency range between 20 khz and 300 GHz. another is which quantity, voltage or current is being amplified; amplifiers can be divided into voltage amplifiers, current amplifiers transconductance (i=)amplifiers, and transresistance amplifiers. a further distinction is whether the output is a linear or nonlinear representation of the input. Amplifiers can also be categorized by their physical placement in the signal chain(信号通路,信号链) 上海海事大学息工程学院上海海事大学信息工程学院 Background ◼ The types of amplifiers can be categorized in different ways. One is by the frequency of the electronic signal being amplified; audio amplifiers amplify signals in the audio (sound) range of less than 20 kHz, RF amplifiers amplify frequencies in the radio frequency range between 20 kHz and 300 GHz. Another is which quantity, voltage or current is being amplified; amplifiers can be divided into voltage amplifiers, current amplifiers, transconductance(跨导) amplifiers, and transresistance amplifiers. A further distinction is whether the output is a linear or nonlinear representation of the input. Amplifiers can also be categorized by their physical placement in the signal chain（信号通路，信号链）