① Benefits: Both high-frequency circuits and low-frequency power supply circuits have voltage gain and output power harvesting effects. Resonant differential amplification circuits refer to the resonant frequency f0, and for fiber optic broadband differential amplification circuits, they refer to a frequency range.

　　② Pass band: The concept is quite different from that of low-frequency power circuit boards. For resonant differential amplification circuits, most of them are the values between the two corresponding frequencies when the normalized vibration amplitude of the resonance frequency f0 decreases to 0.707; For fiber optic broadband amplification circuits, it refers to the corresponding meaning relative to a certain frequency.

　　③ Selectivity: Selectivity is mainly aimed at resonant amplification circuits, which characterizes the selection of useful signals and the suppression ability of useless signals in the circuit. It is usually measured using rectangular coefficient and suppression ratio based on the resonant characteristic curve of the circuit.

　　④ Noise coefficient: When amplifying the operation of a circuit, fluctuations will move irregularly due to certain factors, and the formation of noise inside the circuit will affect the quality of the signal. This effect is usually described by the ratio of signal power PS to noise power PN (SNR). The coefficient of noise is the comparison between input signal noise and output signal noise.

　　⑤ Stability: High frequency circuit board stability refers to the stability of its main performance when the working state or working conditions change. When the temperature of the environment changes or the voltage of the power supply fluctuates, it will affect the normal operation of the amplified circuit DC; The parameters of circuit components will also change accordingly, which will lead to changes in the gain of the amplification circuit, frequency transfer of the center, and sudden changes in the resonance curve. Ultimately, it may result in a fundamental inability to function properly.