An amplifier in electronic components is a core device used to enhance the amplitude, power, or current of electrical signals. Its function is to amplify the characteristics of the input signal (such as voltage, current, power) in a specific ratio while maintaining the basic form of the signal (such as waveform, frequency). Amplifier is widely used in communication, audio processing, sensor signal conditioning, control systems and other fields, and is a key component of modern electronic systems.
1、 Core types and characteristics of amplifiers
2、 Key performance parameters
1. Gain
-Voltage gain \ (A_v=V_ {\ text {out}}/V_ {\ text {in}} \) (unit: dB)
-Power gain \ (A_p=P_ {\ text {out}}/P_ {\ text {in}} \) (unit: dB)
Example: The audio amplifier has a gain of 40dB (100x voltage amplification).
2. Bandwidth
-The effective operating frequency range of the amplifier (-3dB point definition), such as the operational amplifier GBW (gain bandwidth product) of 10MHz.
3. Input/output impedance
High input impedance (such as 1M Ω) reduces signal source load effects, while low output impedance (such as 50 Ω) enhances driving capability.
4. Linearity and distortion
-Total harmonic distortion (THD)<0.01% (high fidelity audio), and third-order intermodulation point (IIP3) reflects the degree of nonlinear distortion.
5. Efficiency (power amplifier)
-Class D amplifiers have an efficiency of over 90%, while Class AB amplifiers have an efficiency of about 50%~70%, which affects heat dissipation design and energy consumption.
3、 Typical Circuit Topology
1. Classic configuration of operational amplifier
Inverted amplifier: \ (V_ {\ text {out}}=- (R_f/R_ {\ text {in}}) \ cdot V_ {\ text {in}} \)
In-phase amplifier: \ (V_ {\ text {out}}=(1+R_f/R_ {\ text {in}}) \ cdot V_ {\ text {in}} \)
Integrator/differentiator: dynamic signal processing is achieved through capacitors/inductors.
2. Classification of power amplifiers
Class A: Linear optimal, low efficiency (<30%), used for high fidelity audio.
Class B/AB: push-pull structure, moderate efficiency, balancing linearity and power consumption.
Class D: Switch mode, efficiency>90%, suitable for portable devices.
4、 Application scenarios and cases
1. Consumer electronics
Mobile phone: LNA amplifies RF signals, Class D amplifier drives speakers.
Bluetooth earphones: Low power operational amplifiers process audio signals to improve signal-to-noise ratio (SNR).
2. Industrial control
PLC system: Differential amplifier suppresses common mode noise in factory environment.
Sensor interface: The instrument amplifier amplifies the mV level signal of the pressure/temperature sensor.
3. Medical equipment
ECG monitoring: High CMRR amplifier extracts small electrocardiogram signals (0.5-4mV).
Ultrasound imaging: Broadband RF amplifier processes high-frequency echo signals.
4. Communication system
5G base station: GaN RF amplifier supports millimeter wave (28GHz) high-power output.
Satellite receiver: Low noise amplifier (LNA) reduces the system noise figure.
5、 Selection Guide
1. Signal type
Low frequency/DC: Precision operational amplifiers (such as ADI AD8629, offset voltage<1 µ V) are preferred.
High frequency/RF: Choose a GaAs/GaN RF amplifier (such as Qorvo QPA2211).
2. Power demand
Small signal: Low power operational amplifier (such as TI TLV904, supply voltage 1.8-5.5V).
High power: Class D amplifier (such as Infineon MA12070, output 100W).
3. Environmental requirements
High temperature/vibration: Automotive grade amplifier (such as STMicro TSV771, AEC-Q100 certification).
Low noise: JFET input operational amplifier (such as TI OPA1612, noise density 1.1nV/√ Hz).
6、 Future Trends
Wide bandgap semiconductor: GaN/SiC amplifier enhances high-frequency and high-temperature performance, used for 6G communication and electric vehicles.
Integration: SoC built-in amplifier (such as TI MSP430 microcontroller integrated PGA) simplifies circuit design.
AI optimization: Adaptive amplifiers dynamically adjust parameters through machine learning to adapt to changing signal environments.
Summary: An amplifier is the "signal engine" of an electronic system. Through targeted selection and circuit design, signal integrity can be optimized and system performance can be improved. Understanding its types, parameters, and application scenarios is one of the core skills of electronic engineers.