Side-by-side comparison
| Parameter | Schottky | Normal PN Junction Diode |
|---|---|---|
| Junction type | Metal-semiconductor (e.g., platinum silicide on n-Si) | p-type semiconductor on n-type semiconductor |
| Forward voltage (Vf) | 0.2–0.4 V (BAT85, 1N5819) | 0.6–0.7 V (1N4148, 1N4007) |
| Reverse recovery time (trr) | < 10 ns; essentially no minority carrier storage | 4 µs (1N4148); up to 30 µs (1N4007) |
| Switching speed | Very fast; suitable above 1 MHz | Limited to < 1 MHz for signal diodes |
| Reverse leakage current | Higher; µA to mA at room temperature | Lower; nA range for 1N4148 |
| Maximum reverse voltage (PIV) | 20–200 V; lower than equivalent PN diode | Up to 1000 V for 1N4007 |
| Temperature sensitivity | Leakage doubles approximately every 10°C | Less sensitive to temperature in leakage |
| Power rectification use | Limited by low PIV and high leakage at temperature | Preferred for 50 Hz mains rectification (1N4007) |
| HF rectification / detector | Preferred; low Vf and fast recovery | Poor at HF due to long trr |
| Typical components | BAT85, 1N5819, BAT54, SB560 | 1N4148 (signal), 1N4007 (power), BY127 |
Key differences
The Schottky diode conducts majority carriers only — electrons crossing from n-silicon to the metal — so when reverse biased, there is no stored minority charge to sweep out; recovery is nearly instantaneous, under 10 ns for a BAT85. The 1N4148 PN diode must sweep out stored minority holes during reverse recovery, introducing a 4 µs tail at 1 MHz that causes significant power loss in a switching converter. However, Schottky leakage is 10–100× higher than a PN diode, making it unsuitable for precision rectifiers where offset matters. Schottky forward voltage of 0.3 V versus 0.7 V for silicon PN saves 0.4 V per diode drop — meaningful in a 3.3 V system.
When to use Schottky
Use a Schottky diode when switching frequency is above 100 kHz or forward voltage drop must be minimised — for example, a 1N5819 in the freewheeling diode position of a 100 kHz buck converter where fast recovery prevents cross-conduction losses.
When to use Normal PN Junction Diode
Use a standard PN junction diode when reverse voltage is high or leakage must be minimal — for example, a 1N4007 rectifying 230 V AC mains (PIV = 1000 V) in a linear power supply bridge rectifier.
Recommendation
For high-frequency switching circuits and low-voltage rectification, always choose a Schottky diode — the BAT85 or 1N5819 is the right part. For mains rectification and any circuit where high PIV or low leakage matters, choose the standard PN diode like the 1N4007. The 0.3 V versus 0.7 V forward drop difference is a key number — memorise it.
Exam tip: Examiners ask you to explain the absence of reverse recovery time in Schottky diodes by reference to majority carrier conduction — draw the energy band diagram showing the metal-semiconductor barrier and explain that minority carriers are not injected.
Interview tip: Interviewers at power electronics companies ask you to justify the choice of Schottky diode in a SMPS freewheeling position and calculate the power loss reduction per diode when Vf drops from 0.7 V to 0.3 V at a given load current.