Typical coupling method inside isolation amplifiers In most mainstream isolation amplifier ICs and modules, which coupling method is commonly used to transfer the signal across the galvanic isolation barrier while maintaining high common-mode voltage tolerance?

Introduction / Context:
Isolation amplifiers transfer signals between high-potential-difference domains while preventing DC conduction. Choosing an appropriate coupling method is essential for safety certifications, noise immunity, bandwidth, and cost.

Given Data / Assumptions:

• Focus on common industrial/medical isolation amplifiers.
• Goal: galvanic isolation across a rated barrier (kV range).
• Signal integrity and safety standards are priorities.

Concept / Approach:
Widely used coupling methods include optical (LED-photodiode/phototransistor), magnetic (micro-transformers), and capacitive (high-voltage capacitors). Among these, optical coupling has historically been the most common, offering robust isolation and simplicity. It converts the electrical signal to light and back to an electrical signal on the secondary side through a transparent isolation barrier.

Step-by-Step Solution:

Verification / Alternative check:
A survey of commercial isolation amplifiers reveals many optically coupled solutions, alongside notable transformer- and capacitive-coupled families. The question asks for a commonly used method; optical coupling fits best.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming one method is exclusive. While optical is common, designers also use transformer or capacitive isolation depending on bandwidth and integration needs.

Final Answer:
Optical coupling (e.g., opto-isolator or LED/photodiode link)