An amplifier is an electronic circuit that amplifies an input signal and outputs it to a load. Amplifiers can be divided into many types according to different classification standards. Below we will introduce in detail the various classifications and characteristics of amplifiers.

Classification according to the way of work

1. Class A amplifier

Class A amplifier is one of the most basic amplifiers, which adopts single-tube or double-tube structure, and has the advantages of simplicity, reliability, and low cost. The characteristic of the class A amplifier is that there is current flowing in the entire signal cycle, that is, the current flows in the positive half cycle and the negative half cycle of the input signal, so the efficiency of the class A amplifier is relatively low, generally only about 50%. Due to the flow of current, a large crossover distortion will be generated, and the distortion needs to be compensated by a negative feedback circuit.

2. Class B amplifier

A class B amplifier is an amplifier that only has current flowing in the positive half cycle or the negative half cycle. It is usually composed of two complementary transistors, one of which is responsible for amplifying the positive half cycle signal, and the other is responsible for amplifying the negative half cycle signal. This structure can effectively improve the efficiency of the amplifier, which can theoretically reach 78.5% efficiency. However, Class B amplifiers produce large cut-off distortion, which requires cross-coupling circuits to eliminate the distortion.

3. Class AB amplifier

A class AB amplifier is a combination of class A and class B amplifiers. It uses two complementary transistors, one of which has current flowing through the entire signal cycle, and the other has current only in the positive half cycle or negative half cycle of the signal. flow past. This structure can effectively improve the efficiency of the amplifier and reduce the influence of crossover distortion and cut-off distortion, so it is widely used in various audio amplifiers.

4. Class C amplifier

A Class C amplifier is an amplifier that only has current flow when the top or bottom of the input signal is present. Because only a part of the signal is amplified, the efficiency of Class C amplifiers is very high, theoretically 100% efficiency can be achieved. However, Class C amplifiers can generate large distortion and harmonics, so they are usually only used for amplification of radio frequency signals.

5. Class D amplifier

A Class D amplifier is a digital amplifier that converts an analog signal into a digital signal, and then uses PWM (pulse width modulation) technology to convert the digital signal into an analog signal output. Because digital signals have the advantages of high precision, low noise, and high speed, Class D amplifiers have high efficiency and low distortion.

Classification according to frequency response

1. Low frequency amplifier

A low-frequency amplifier is an amplifier suitable for amplifying low-frequency signals. It is usually used in audio amplifiers, power amplifiers, DC amplifiers and other fields. Due to the narrow frequency range of low-frequency signals, the design of low-frequency amplifiers is relatively simple.

2.IF Amplifier

An intermediate frequency amplifier is an amplifier suitable for amplifying intermediate frequency signals. It is usually used in radio, television, radar and other fields. The frequency range of the intermediate frequency signal is relatively wide, usually between several hundred kilohertz to several megahertz, so the design of the intermediate frequency amplifier needs to consider issues such as bandwidth, gain, and stability. 3. High frequency amplifier

A high-frequency amplifier is an amplifier suitable for amplifying high-frequency signals. It is usually used in radio communication, satellite communication, radar, navigation and other fields. The frequency range of high-frequency signals is very wide, usually ranging from tens of megahertz to several gigahertz, so the design of high-frequency amplifiers needs to consider issues such as bandwidth, stability, and noise.

Classification according to magnification

1. Low Gain Amplifier

A low-gain amplifier is an amplifier with a small output voltage, which is usually used for signal front-end amplification, such as the amplification of sensor signals. Low-gain amplifiers are characterized by high input resistance, low output resistance, and narrow bandwidth.

2. Medium Gain Amplifier

A medium-gain amplifier is an amplifier with a large output voltage, typically used in signal processing and control systems. Medium gain amplifiers are characterized by wide bandwidth, good stability, and low distortion.

3. High gain amplifier

A high-gain amplifier is an amplifier with a very large output voltage, usually used in audio, video, radio frequency and other fields. High-gain amplifiers are characterized by wide bandwidth, low distortion, and low noise.

Classification by Application

1. Power amplifier

A power amplifier is an amplifier specially used to drive a load, and is usually used in audio, television, radio communication and other fields. The power amplifier is characterized by high output power, high efficiency, and low distortion.

2. Differential amplifier

A differential amplifier is an amplifier used to compare two input signals, and is usually used in differential signal amplification, filtering, data conversion, and other fields. The differential amplifier is characterized by suppressing common-mode interference, enhancing signal quality, and improving system stability.

3. Voltage Controlled Amplifier

A voltage-controlled amplifier is an amplifier that can control the output current according to the input voltage, and is usually used in the fields of automatic control, regulation and protection. The voltage controlled amplifier is characterized by high precision, fast response and good reliability.

4. Operational amplifier

An operational amplifier is an amplifier used for operations such as operations, filtering, and comparison, and is usually used in analog computers, sensor signal processing, and other fields. Operational amplifiers are characterized by high precision, good linearity, and high reliability.

In short, the amplifier is a very important electronic component, which has been widely used in various fields. Different types of amplifiers have different characteristics and scope of application, and it is necessary to select a suitable amplifier according to the specific application scenario.

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