Sigma–delta (delta–sigma) modulation – is one common form specifically designed to convert a continuous-time analog input into a 1-bit, noise-shaped bitstream for subsequent digital filtering (i.e., an A/D front end)?

Introduction / Context:
Sigma–delta modulators underpin many modern high-resolution ADCs used in audio, instrumentation, and sensor interfaces. They oversample the input and shape quantization noise out of band, producing a high-rate 1-bit stream that a digital decimation filter converts into multi-bit samples.

Given Data / Assumptions:

• Analog input is band-limited relative to the modulator clock.
• A 1-bit quantizer (comparator) and a feedback DAC form the core loop with an integrator.
• Digital filtering/decimation follows the modulator.

Concept / Approach:
A sigma–delta modulator integrates the error between the analog input and a 1-bit DAC's feedback, feeding the result to a 1-bit quantizer. The output bitstream contains the input information plus shaped noise (pushed to higher frequencies). Later, a digital low-pass filter and downsampler recover a precise digital representation of the analog signal in the desired bandwidth, completing the A/D path.

Step-by-Step Solution:

Verification / Alternative check:
Audio ADCs (for example, 24-bit) and precision sensor ADCs commonly specify a sigma–delta front end followed by digital filtering, confirming the A/D purpose of this architecture.

Why Other Options Are Wrong:
The architecture is not limited to D/A tasks; it measures amplitude over time, not just frequency; it is applicable to many sensor types, not only thermocouples.

Common Pitfalls:
Confusing the 1-bit stream with low resolution—after decimation, effective resolution can be very high within the signal band.

Final Answer:
Correct