In a standard power-supply block diagram (AC mains → transformer → rectifier → filter → regulator → load), which functional block specifically indicates a smoothed DC output by reducing ripple from the rectifier stage?

Introduction / Context:
Power supplies convert AC mains into a usable DC voltage. After the diode rectifier creates a pulsating DC waveform, additional circuitry is needed to “smooth” the ripple and produce a steadier DC before fine regulation. This question checks whether you can correctly identify the block that performs the smoothing function in the classic supply chain.

Given Data / Assumptions:

• Typical linear power-supply flow: transformer → rectifier → filter → regulator.
• Rectifier output is pulsating DC with significant ripple.
• Filter networks (usually capacitors and sometimes inductors) reduce ripple amplitude.
• Regulator subsequently stabilizes the voltage against line/load variations.

Concept / Approach:
The filter stage is designed to attenuate the AC ripple component present at the rectifier output. Common filters include a large reservoir capacitor (C filter), an LC choke-input filter, or a π (C–L–C) network. While a regulator improves voltage stability and load/line regulation, the chief “smoothing” action that turns pulsating DC into a much flatter DC is the job of the filter.

Step-by-Step Solution:
Rectifier: converts AC to pulsating DC (high ripple).Filter: capacitor(s)/inductor(s) charge and discharge to fill gaps between peaks, reducing ripple.Regulator: trims and stabilizes the already-smoothed DC to a precise level.Therefore, the block indicating a smoothed DC output is the filter stage.

Verification / Alternative check:
Observe waveforms on an oscilloscope: rectifier output shows large ripple; adding a filter capacitor markedly flattens the waveform. Adding a regulator then further stabilizes the DC level with minimal remaining ripple.

Why Other Options Are Wrong:

• Transformer: Only changes voltage level and isolation, not smoothing DC ripple.
• Rectifier: Produces pulsating DC rather than smooth DC.
• Regulator: Stabilizes DC level but relies on a filtered input for best performance.

Common Pitfalls:

• Assuming the regulator alone removes ripple. It reduces ripple further but is not the primary smoothing block.
• Confusing “rectification” (direction control) with “filtering” (ripple reduction).

Final Answer:
filter