Which of the following best describes a buffer amplifier?

A buffer amplifier is specifically designed to amplify an input signal without inverting its phase. Its primary function is to provide a high input impedance and a low output impedance, which allows it to effectively isolate different stages of a circuit while preserving the original signal's characteristics.

When a buffer amplifier receives an input signal, it amplifies it to a suitable level for further processing, but it does not introduce any phase shift. This characteristic is essential in many electronic applications, such as when interfacing high-impedance sources with low-impedance loads or when driving longer cables in audio and video applications.

In contrast, other descriptions do not apply to buffer amplifiers. While some amplifiers may regulate current or control voltage, that is not the primary function of a buffer. Furthermore, inverting signals is a feature of specific amplifier designs, such as inverting operational amplifiers, and is not applicable to buffer amplifiers. Overall, the nature of a buffer amplifier to amplify without changing the signal's phase is what makes it indispensable in various electronic circuits.