SnapLED150 Red-Orange LED I-V Curve Tracer

Application

This circuit characterizes the SnapLED150 red-orange LED by sweeping the voltage bias across the LED from reverse bias into forward conduction. It is useful for estimating the LED forward knee and checking diode polarity before using the part in an indicator or display circuit.

Design Context

VBIAS is connected directly across the LED under test through the current probe. The DC sweep moves VBIAS from -1 V to +3 V in 20 mV steps, so the chart shows how LED current changes as the applied diode voltage crosses from reverse bias into forward conduction. The cathode is tied to the common return, so positive sweep values forward-bias the LED and negative values reverse-bias it.

Expected Behavior

For negative bias values, Id should remain very small because the LED is reverse biased below breakdown. Near zero bias, current should stay close to zero. As the sweep approaches the red-orange LED forward knee, current rises quickly and the dynamic LED symbol brightens as forward current increases.

Key Values

• Sweep source: VBIAS
• Sweep range: -1 V to +3 V
• Sweep increment: 0.02 V
• Measured voltage: Vd
• Measured current: Id
• LED model: Lumileds SnapLED150 / A1SS-O612

Suggested Experiments

• Narrow the sweep around 1.5 V to 2.2 V to inspect the forward knee in more detail.
• Reduce the sweep stop value if you want to focus on low-current indicator operation.
• Compare this curve against a green LED or silicon switching diode to see how material and color change forward voltage.

Featured Component

The SnapLED150 Red-Orange LED is the diode under test. Its SPICE model captures the basic electrical forward-conduction behavior of the Lumileds A1SS-O612 red-orange indicator LED so the chart can show current versus voltage across the device.