LED forward-voltage range: Typically, the forward voltage drop of a light-emitting diode (LED) at nominal current falls within which range?

Introduction / Context:
LEDs are semiconductor diodes that emit light when forward-biased. Their forward voltage (Vf) depends on semiconductor material and emitted color. Knowing typical ranges helps with resistor sizing, driver selection, and power budgeting in practical circuits.

Given Data / Assumptions:

• Nominal operating currents (for example, 5–25 mA for indicator LEDs).
• Common materials and colors (red, green, blue, white).
• Room-temperature operation, ignoring extreme thermal drift.

Concept / Approach:
Red/amber LEDs (AlGaInP or similar) often have Vf ≈ 1.6–2.2 V. Green/yellow are around 2.0–2.4 V (material-dependent). Blue/white devices (GaN-based) typically sit around 2.8–3.6 V. Therefore, a broad but realistic range is about 1.5 V to 3.7 V for common indicator LEDs at nominal currents.

Step-by-Step Solution:

Verification / Alternative check:
Check any LED datasheet: forward voltage vs current curves show values in the above bands, with temperature shifting Vf downward as junction temperature rises.

Why Other Options Are Wrong:

• 0.7–1.1 V: Typical of silicon/germanium rectifier diodes, not LEDs.
• 1.0–3.0 V: Too low for many blue/white devices at nominal currents.
• 3.7–5.0 V: Overstates typical Vf; only high-current or specialty LEDs may approach parts of this range.

Common Pitfalls:
Using a single “standard” Vf for all LEDs; ignoring current dependence and temperature effects; forgetting series resistors or constant-current drivers are required.

Final Answer:
1.5 V to 3.7 V