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Answer: Reverse biased is when a diode is wired to not conduct when a voltage is applied in a certain direction. It’s also when a specially made (zener) diode will conduct at a much higher voltage than while forward biased. A diode/LED is reverse biased when the Anode is more negative than a cathode. Whereas they are forward biased (conduct easily) when the Anode is more positive than the cathode.
If you see a rectifier diode in a circuit, and it looks like it isn’t doing anything useful, then it is likely being used as reverse power polarity protection.
If an LED doesn’t light up when it looks like it is wired correctly and enough voltage is making to the LED to light up, then there is a good chance that the LED is wired backwards (reverse biased). Simply remove the LED and turn it around before returning it, and it should light up.
Rectification:
Many electronics will be damaged if you apply the power backwards (positive terminal where negative is suppose to go, and negative terminal where positive is suppose to go). You will tend to see a rectifier diode whose Anode is wire to where the positive side of the power supply is suppose to go (usually directly) and the Cathode headed towards where the negative supply is suppose to go. Usually the load is between the diode’s Cathode and the negative supply when it is ground.
Zener voltage regulator:
Zener diodes build up a certain voltage (their zener voltage) when a higher voltage (must have something limiting current) is applied across the zener diode. The zener diode passes current as needed to maintain the voltage. It is best to use the zener diode to create a signal voltage instead of as a power regulator by itself.
- Power (voltage) limitation:
- Signal voltage:
Good pages to check out next:
Polarity indicator:
You can get a visual indication of whether the supply voltage is applied in the correct direction by having a couple parallel LEDs wired in opposite directions, and one or more current limiting resistors.
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