low-frequency amplifier

例句：

1. 1.The low-frequency amplifier is used to amplify signals at very low frequencies.
   低频放大器用于放大非常低频的信号。
2. 2. In the medical field, low-frequency amplifiers are often used to monitor heart rates.
   在医疗领域，低频放大器通常用于监测心率。
3. 3. The low-frequency amplifier was designed to improve the clarity of audio signals.
   低频放大器被设计来提高音频信号的清晰度。