Function of an isolation amplifier: Does it provide galvanic isolation (for both DC and AC paths) between input and output so that signals can be transferred without a conductive connection?

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
An isolation amplifier is designed to pass an analog signal across an isolation barrier without a direct electrical connection. This barrier protects systems from high common-mode voltages, ground loops, and transients, and it enables safe interfacing to hazardous or noisy domains. The isolation typically applies to both DC and AC components of the signal path, depending on internal coupling (optical, capacitive, or transformer-based with modulation/demodulation).


Given Data / Assumptions:

  • Goal is to transfer an analog signal while breaking the DC conductive path.
  • Applications include medical, industrial, power electronics, and precision metrology.
  • Isolation barrier must meet safety and performance ratings (withstand voltage, creepage/clearance, CMRR).
  • Signal integrity (linearity, bandwidth, noise) must be preserved through the barrier.


Concept / Approach:
Isolation amplifiers encode the input signal and convey it across an isolation barrier via light, electric field, or magnetic coupling. A corresponding receiver reconstructs the analog output referenced to the isolated side. Proper modulation schemes and feedback maintain linearity and bandwidth, ensuring both AC content and DC levels can be faithfully reproduced, providing full galvanic isolation between input and output grounds.


Step-by-Step Solution:

Define isolation: no direct conductive path for DC or AC ground currents.Choose coupling: optical (LED + photodiode), capacitive, or transformer with modulation.Ensure ratings: isolation voltage, CMTI, and regulatory compliance.Outcome: accurate, isolated replica of the input on the output side.


Verification / Alternative check:
Differential (non-isolated) amplifiers can reject common-mode voltage but cannot tolerate unlimited DC offsets or ground faults. Isolation amplifiers handle both by physically separating grounds while maintaining signal fidelity.


Why Other Options Are Wrong:

Only DC isolation: many isolation amps pass AC content through modulation and demodulation.Only RF isolation: isolation spans the device bandwidth, not just RF.Isolation only if output is battery powered: isolation is inherent to the barrier, not power source.Incorrect: contradicts the device’s purpose.


Common Pitfalls:
Confusing isolation with simple differential measurement, overlooking isolation capacitor ratings, or ignoring bandwidth/linearity limits of the isolation scheme.


Final Answer:
Correct

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