In regulated power supplies used in electronics, the regulator's job is to prevent the DC output voltage from drifting when there are changes in the AC line voltage (mains variations) and/or changes in the load current drawn by the connected circuit. Which factor(s) are regulated against?

Introduction:
Regulated power supplies are designed to provide a stable DC output even when the input conditions or the load conditions vary. This question tests understanding of two primary disturbances: fluctuations in the AC mains (line regulation) and changes in the load current (load regulation).

Given Data / Assumptions:

• Output required: steady DC voltage for electronic circuits.
• Disturbances: AC line variations and load current changes.
• Typical regulator types: linear (series, shunt) and switch-mode (buck, boost, etc.).

Concept / Approach:
Line regulation measures how much the output changes when the input (line) voltage changes. Load regulation measures how much the output changes as load current varies from minimum to maximum. A good regulator minimizes both, maintaining a nearly constant output voltage under real-world conditions.

Step-by-Step Solution:
Identify disturbances: input (line) and output (load) changes.Define line regulation: ΔV_out per ΔV_in should be small.Define load regulation: ΔV_out per ΔI_load should be small.Regulated supplies implement feedback to correct deviations caused by either disturbance.

Verification / Alternative check:
Datasheets specify both line regulation (e.g., mV/V) and load regulation (e.g., mV/A or % from no-load to full-load); high-quality supplies exhibit tight figures in both metrics, proving that regulation targets both mains and load changes.

Why Other Options Are Wrong:

• line voltage: Incomplete; ignores load changes.
• supply load: Incomplete; ignores line variations.
• frequency: Frequency tolerance alone is not the main regulation target.
• temperature only: Temperature affects drift but is not the principal definition of regulation here.

Common Pitfalls:

• Confusing ripple reduction (filtering) with regulation (feedback control).
• Assuming only line changes matter; load transients are equally important.

Final Answer:
both line voltage and supply load