What role does a band-pass filter play in a circuit?

A band-pass filter is specifically designed to allow a certain range of frequencies to pass while attenuating frequencies outside this range. This characteristic is essential in various applications, such as in communication systems where it is important to isolate specific signals from a mixture of different frequencies. For example, a band-pass filter can be used in radio receivers to allow only the desired frequency channel to be processed, while filtering out both higher and lower frequencies that might interfere with the desired signal.

In contrast, other options describe different types of filter behaviors. One option states that all frequencies can pass, which is characteristic of a flat response filter or a low-pass filter depending on the context. Another option suggests that all frequencies are stopped, which would describe a notch filter or simply an open circuit. Finally, stating that a filter amplifies the signal without altering frequencies describes an ideal amplifier rather than a filter's functionality. Therefore, the defining function of a band-pass filter is its ability to selectively permit a specific band of frequencies to pass while blocking those outside that band.