The invention provides a limiting amplifier, comprising an amplifying module and a sampling module, wherein the amplifying module comprises two main signal input ends, two amplitude limiting output ends, a plurality of amplifiers, which are connected between the two main signal input ends and the two amplitude limiting output ends in series, and a plurality of groups of sampling output ends corresponding to the amplifiers; and the sampling module comprises three input ends, a plurality of groups of sampling input ends corresponding to the amplifiers, two sampling output ends, a first resistor, a second resistor and a power supply end; the two input ends of the sampling module are respectively connected with the two main signal input ends, and the other input end of the sampling module is connected with a bias signal; each group of sampling input ends of the sampling module are respectively connected with each group of sampling output ends of the amplifying module, and the two sampling output ends are respectively connected with one end of the first resistor and one end of the second resistor, and the other ends of the first resistor and the second resistor are connected with the power supply end. Each group of sampling input ends and each group of sampling output ends of the limiting amplifier are connected correspondingly for sampling, so that the the sampling accuracy is ensured.