Schottky diode
A Schottky diode rectifies current with a low forward drop (~0.2–0.4 V) and switches between on and off so fast that it's the workhorse of switching power supplies, OR-ing rails, and ideal-diode emulation.
Instead of a P–N silicon junction, a Schottky uses a metal anode pressed onto an N-type semiconductor. The barrier is much lower than P–N, so it conducts with less voltage drop. There are also no minority carriers to recombine, so reverse recovery is nearly zero.
In plain terms
Imagine a regular diode loses 0.7 V like a long highway tollbooth, while a schottky pays only 0.3 V — and the tollbooth opens and closes almost instantly.
Why designers use it
- Rectify the output of a buck/boost converter without burning a watt as heat.
- OR two power rails together so the higher one wins, with minimal drop.
- Bypass slower diodes during fast-switching transients.
- Protect against reverse-polarity battery insertion with low loss.
Best for
- Buck rectifier
- OR-ing
- Reverse-polarity guard
Key specifications
- Vf @ 1 A: 0.25 V – 0.55 V
- Reverse voltage: 10 V – 200 V
- Reverse leakage: 0.1 – 5 mA (Higher than silicon p-n)
- Reverse recovery: <1 ns (Effectively zero)
- Forward current: 0.1 A – 100 A
When not to use it
- When reverse leakage matters (Schottkys leak more than P–N).
- When the rail exceeds the part's reverse rating — Schottkys typically max out below 200 V.
- When you need a Zener-style clamp — use a real Zener or TVS.
Common mistakes
- Picking a 20 V Schottky for a 24 V boost output and watching the diode fail.
- Ignoring leakage at hot temperatures — leakage roughly doubles every 10 °C.
- Missing the SOA — power Schottkys still need heat-sinking.
Where you will find it
- A solar charge controller uses a Schottky diode to prevent the battery from back-feeding current into the solar panel at night: the 0.3 V forward drop wastes far less power than the 0.7 V of a silicon diode would, which matters when the panel is barely generating 1 A in cloudy conditions.
- A laptop with two USB-C ports uses a pair of Schottky diodes to OR the power rails from each port: whichever port delivers the higher voltage forward-biases its diode and supplies the system, while the lower-voltage port's diode stays reverse-biased — no relay or control logic needed.
- A brushed motor's H-bridge uses four Schottky flyback diodes across the switching MOSFETs: each time the motor coil's magnetic field collapses, the Schottky clamps the inductive spike to within one forward drop above the supply rail, protecting the FETs from the voltage that would otherwise punch through their gate oxide.
A short history
The Schottky diode is named after German physicist Walter Schottky, who in 1938 derived the theoretical model of metal-semiconductor barriers (now called the Schottky barrier). Practical silicon Schottky diodes were commercialised in the 1960s as 'hot-carrier' diodes in microwave detector applications. Because conduction is by majority carriers (electrons) only, with no minority-carrier storage, Schottky diodes have nanosecond reverse-recovery times and forward voltages of just 0.2–0.4 V—half that of silicon p-n diodes. They are the standard rectifier in low-voltage switch-mode power supplies, OR-ing diodes in redundant power paths, and signal-clamp applications throughout modern electronics.
Good to know
- Schottky diodes use a metal-semiconductor barrier, not a p-n junction, so there are no minority carriers to clear — switching is essentially instantaneous.
- The ~0.3 V forward drop saves real power in low-voltage rectifiers; in a 5 V supply it's the difference between 6 % and 14 % loss.
- Walter Schottky predicted the metal-semiconductor barrier effect in 1938; commercial silicon Schottky rectifiers arrived around 1970.