Reverse-Biased Light Sensor

Application

Use this bias circuit as a simple ambient light sensor input.

Design Context

The photodiode is reverse biased and light-generated current is converted to a sense voltage by the load resistor.

Expected Behavior

The table updates as light level changes. Higher light increases photocurrent and changes Vphoto.

Key Values

• V1 is 5 V.
• R1 is 47 k.
• D1 uses 100 uA maximum photocurrent.

Suggested Experiments

• Change light from 0% to 100%.
• Increase R1 for more voltage sensitivity.
• Compare Vphoto at different light levels in the table.

Featured Component

The photodiode component models light-generated current in addition to the dark diode junction.