Using a Protection Diode to Safeguard Circuits & Devices

Current that flows opposite its intended direction can damage many electronic devices. Reversed voltage and current is a common mistake when you're working with DIY electronics or any wiring that you might accidentally plug in backward. If you've made this mistake before, you may want to implement a solution in your design. You can use a "fool's diode"―also called a protection diode―to safeguard your device.

How Does a Protection Diode Work?

Diodes are a type of semiconductor that allow current to flow through them in one direction only. Therefore, we can use diodes to block reversed voltages from moving current backwards through a system, sparing sensitive parts elsewhere in the device. We should note that a fool's diode setup doesn't correct the reversed voltage. So while you won't be able to turn your device on, at least you'll be able to swap things out and give it another try. The simplest installation installs the diode in series with the other components:

Because the diode's ability to protect other components comes from its "stopping power," you'll need to double-check the peak reverse voltage, a specification that defines how much voltage the diode can absorb before breaking down and allowing current to pass. Diodes coded 1N400x are intended for use as a fool's diode, with peak reverse voltage ratings ranging from 50V (1N4001) to 1000V (1N4007).

Schottky Diode: Reverse Voltage Protection with More Power

The biggest drawback of using a protection diode, however, is its forward voltage drop, which is typically around 0.7V. You'll also experience some power loss through heat. One popular method to improve voltage efficiency is to use a Schottky diode, which offers a much smaller forward voltage drop than standard diodes (typically between 0.15V and 0.46V). This tradeoff may or may not be acceptable in your design. In some situations, it would be better to implement mechanical means, such as non-reversible connectors, to improve efficiency.

Another diode-based protection method is to wire a diode in parallel to your main circuit, causing it to block current when voltage is applied correctly. Instead, the voltage travels through the main load. Once reversed, this diode provides an alternate path for electrons, largely bypassing the main circuit and protecting it from these effects. Users need to account for the potential of low resistance and increased current flow to ground when voltage reverses. But since current doesn't flow through the diode in regular operation, this type of circuit works more efficiently than a diode in series.

This type of setup is reminiscent of a "snubber" or "flyback" diode meant to let built-up charges dissipate when a circuit is switched off without damaging components. That configuration is good design practice but isn't meant to guard against human error.


Reverse current and voltage can cause severe damage to the more sensitive components in a circuit. Using a fool's diode, or protection diode, can block or bypass current from the reversed voltages and spare these sensitive components in a device. Protective measures like this can be crucial in the event of human error when hooking up a circuit's positive and negative leads. 

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