What is an isolation amplifier and when would you use one?

• A. A passive device with no gain
• B. A device that couples signals directly across grounds
• C. A device that amplifies signals with no isolation
• D. An amplifier that provides electrical isolation between input and output

Answer: (D)

An isolation amplifier is designed to keep the input side and output side electrically separate while still passing and often amplifying the signal. The key idea is galvanic isolation, meaning there’s no direct electrical path between the two sides. That barrier blocks currents and voltage from one side reaching the other, which helps prevent ground loops, voltage spikes, and noise on one side from contaminating the other. It also allows the input and output to have different ground references or even be in different locations or safety zones.

You’d use one when safety or noise immunity is important, such as connecting sensors in high-voltage or electrically noisy environments, or when the measurement system must tolerate different grounds or potential differences between devices. The isolation barrier is implemented with methods like transformers, opto-isolators, or capacitive coupling, while the signal itself is still amplified or buffered to usable levels on the output side. In short, it provides signal transmission with protection against unwanted current flow between input and output.