Side-by-side comparison
| Parameter | PN Junction | Schottky Diode |
|---|---|---|
| Junction Type | P-type and N-type semiconductor junction | Metal-semiconductor junction (e.g., Platinum silicide on N-Si) |
| Forward Voltage (Vf) | ~0.6–0.7 V (silicon at 1 mA) | ~0.15–0.45 V (varies with current) |
| Reverse Recovery Time (trr) | 1N4007: ~30 µs; 1N4148: ~4 ns | ~0 ns — no minority carrier storage |
| Current Carriers | Both majority and minority carriers | Majority carriers only (electrons in N-type) |
| Leakage Current | Low — nA range at room temperature | Higher — µA range, increases with temperature |
| Maximum Reverse Voltage | Up to 1000 V (1N4007) | Typically 20–200 V (1N5822: 40 V) |
| Operating Frequency | Up to ~1 MHz with fast types (1N4148) | Up to GHz range in RF applications |
| Temperature Sensitivity | Lower leakage variation with temperature | More sensitive — Vf drops ~2 mV/°C, leakage rises sharply |
| Typical Applications | 50/60 Hz rectification, signal clamping, general switching | SMPS rectifier (>100 kHz), RF mixer, OR-ing circuits |
| Cost | Very low — 1N4007 costs < ₹2 | Slightly higher — 1N5822 costs ~₹8–12 |
Key differences
A PN junction diode injects minority carriers across the junction during forward bias; these must recombine before the diode can block reverse voltage, causing reverse recovery time (trr = 30 µs for 1N4007). A Schottky diode passes current via electrons crossing from semiconductor to metal — no minority carrier injection, so trr ≈ 0. The Schottky forward voltage is also lower (0.3 V vs 0.7 V), cutting conduction losses. The trade-off: Schottky leakage current at reverse bias is 10–1000× higher than a PN junction, and maximum reverse breakdown is limited to ~200 V for most types. The 1N5822 handles 40 V at 3 A — fine for 5 V SMPS outputs, but not for mains rectification.
When to use PN Junction
Use a PN junction diode (1N4007, 1N4148) for mains frequency rectification, signal detection below 1 MHz, and any circuit needing reverse voltage above 200 V. The 1N4148 works to 200 mA at 4 ns switching for signal-level logic applications.
When to use Schottky Diode
Use a Schottky diode (1N5822, BAT54, SS34) in any SMPS operating above 100 kHz, in RF detector circuits up to GHz, or as a low-drop OR-ing diode in power multiplexing circuits where 0.7 V drop from a PN diode would be unacceptable.
Recommendation
Choose Schottky for any switching frequency above 50 kHz or any application where forward voltage drop must stay below 0.4 V. Choose PN junction for mains rectification, voltage clamping, or circuits requiring reverse breakdown above 200 V. The 1N5822 is the workhorse SMPS Schottky; 1N4007 is the workhorse mains rectifier.
Exam tip: Examiners ask why Schottky diodes switch faster — write "majority carrier device, no minority carrier storage, zero reverse recovery time" — and give trr values for a common PN diode like 1N4007 (30 µs) for contrast.
Interview tip: Interviewers at power electronics and SMPS design companies ask the forward voltage comparison — state 0.6–0.7 V for silicon PN vs 0.2–0.4 V for Schottky — and immediately follow with the leakage and reverse voltage trade-off.