In an isolation amplifier that transfers information across an isolation barrier (for example, via a transformer or capacitive coupling), what is the primary role of the oscillator block at the input side of the system?

Introduction / Context:
Isolation amplifiers provide galvanic isolation between input and output for safety and noise immunity. Because transformers and capacitors block dc, isolation systems typically translate the input signal into an ac form, send it across the barrier, and then recover a proportional output on the far side.

Given Data / Assumptions:

• Isolation barrier uses a transformer or capacitors.
• Input of interest may be a slowly varying or dc signal.
• System contains modulator/oscillator, isolation element, and a demodulator/rectifier.

Concept / Approach:
The oscillator generates a carrier, generally at high frequency, onto which the input (even if dc) is modulated. High frequency is preferred to minimize transformer size, improve bandwidth, and ease filtering. After crossing the barrier, synchronous demodulation and filtering recreate a dc (or low-frequency) representation of the original signal.

Step-by-Step Solution:
Create carrier: oscillator produces high-frequency ac.Modulate input: encode the input amplitude onto the carrier.Isolate and transfer: carrier passes through transformer/capacitive barrier.Demodulate/rectify: recover proportional dc on the output side.

Verification / Alternative check:
Block diagrams in isolation-amplifier datasheets show a chopper/modulator feeding a transformer, followed by a demodulator and filter, confirming the oscillator’s role in converting dc to ac for transmission.

Why Other Options Are Wrong:
Low-frequency ac increases size and reduces bandwidth.

Rectification is performed after the barrier, not by the oscillator.

Producing dual-polarity rails is a power-supply function, not the oscillator’s primary role.

Adjusting input common-mode range is handled by front-end design, not the oscillator.

Common Pitfalls:
Confusing isolation power converters with signal-path modulators; although both may use oscillators, the signal path’s primary goal is information transfer, not power delivery.

Final Answer:
convert dc to high-frequency ac