A circuit that can flatten the signal voltage amplitude within a limited range is also called a limiter or clipper. Limiting circuits are often used for: ① shaping, such as cutting off the interference at the top or bottom of the output waveform; ② waveform transformation, such as cutting off the positive pulses in the output signal, leaving only the negative pulses; ③ overvoltage protection, such as strong When the output signal or interference may damage a certain component, a limiting circuit can be connected in front of this component.