Rectifier Diode
Diode
A diode that lets current flow one way only. Used to convert AC to DC and to block reverse current. The everyday power diode.
Schematic symbol
Diode
How rectifier diode appears in a circuit diagram.
Types & variants
Key specs
Forward voltage (Vf)
VDrop when conducting: ~0.7V silicon, ~0.3V Schottky.
Forward current (If)
AAverage current it can pass continuously.
Peak reverse voltage (PIV/VRRM)
VMax reverse voltage it can block before breakdown.
Reverse recovery time (trr)
nsHow fast it stops conducting; matters at high frequency.
Markings
A band/stripe marks the CATHODE (the '-' / bar side of the symbol). Part number printed on body.
Standard values
1N4001-1N4007 (1A, 50-1000V), 1N5817-1N5819 Schottky (1A), 1N5408 (3A), bridge modules KBPC/DB.
How to choose
Pick VRRM well above peak reverse voltage and If above load current (with margin). Use Schottky for low-drop/high-freq, fast-recovery for switching supplies.
Pinout & package
Axial — the printed band marks the cathode
2 leads, POLARISED: anode -> cathode (banded). DO-41/DO-201 axial, SMA/SMB/SMC SMD, bridge has AC/AC/+/- pins.
Example circuits
- Half-wave rectifier
- Full bridge rectifier in a DC supply
- Flyback/freewheel diode across a relay or motor
- Reverse-polarity protection
Common failures
Shorts (passes both ways) from overcurrent/overvoltage, or goes open. A shorted bridge kills the supply.
How to test
Multimeter diode mode: ~0.5-0.7V one way, open (OL) the other. Reads both ways or 0 = faulty.
Substitutes
Any diode with >= current and >= reverse-voltage rating. 1N4007 substitutes any lower 1N400x.