# Reverse polarity diode, which diode is better: SB140 or 1N5819

I want to add reverse voltage polarity protection into my circuit to protect the components in my Arduino robot. But i want to know which diode has the edge on the other: SB140 or 1N5819? Or is there another even better diode for this application?

Here are the datasheets for both mentioned diodes.

From my understanding, i would need to use a diode that has a very low forward voltage drop, but from the datasheets, it seems that both diodes have about the same Vf and both have a Peak Repetitive Reverse Voltage of 40 V which i think should be enough for my battery-powered robot with 12 V. Are there any other characteristics that i should be considering to justify the choice of diode?

• The differences between these diodes are such that for a reverse voltage protection, it does not matter which one you choose. Other suitable diodes have a similar voltage drop. If you want less voltage drop use a series fuse and place the diode in parallel with your circuit such that it conducts (and blows the fuse) when the battery is reverse connected, see: electronics.stackexchange.com/questions/164306/… – Bimpelrekkie Jun 25 '19 at 14:11
• You should be careful using Schottky devices as they have relatively high reverse leakage currents which increases exponentially with temperature. Care is necessary to prevent devices at elevated temperatures going into thermal runaway. The SB140 actually does have a figure showing typical reverse currents vs applied reverse voltage against temperature. – Peter Smith Jun 25 '19 at 14:29
• What type and value of fuse should i use? My power input is 12 DC batteries. From my understanding, if the diode is connected in parallel to the circuit, then current will flow through the battery instead of the circuit when the battery terminals are reversed. I'm wondering what value of fuse would be good to keep the batteries safe. Is there anything i can change in the circuit to manage the reverse current? I checked the datasheet graph and at 25 degrees room temperature and 12 V, the reverse current is about 8uA. Is that a safe value? – WiredMaker Jun 25 '19 at 14:45