In industrial field, pulse signals with different frequencies and sizes need to be amplified and shaped, and then the signals are sent to digital circuits for processing through optocoupler isolation circuits. Due to all kinds of interference in the field, especially the serious interference in * * * mode, ordinary single-ended operational amplifier can not accurately amplify the signal. INA 1 18, as a new instrument amplifier with high precision, wide frequency band and high * * mode rejection ratio, is very suitable for signal amplification. It consists of diode voltage limiting input circuit, INA 1 18 differential amplifier circuit and LM324 hysteresis comparison circuit. INA 1 18 not only works in a wide frequency band, but also has high anti-interference ability. This is a very convenient instrumentation amplifier.