Diode breakdown voltage is the reverse-bias voltage at which reverse current rises sharply. It is a measured junction characteristic, not automatically a safe operating voltage. For an ordinary rectifier, stay below its published reverse-voltage rating. A Zener diode is different because it is designed to operate in controlled reverse breakdown.
The correct value depends on the diode type and on the exact datasheet parameter.
| Diode type | Parameter to read | What it means | Verified example |
|---|---|---|---|
| Ordinary PN or switching diode | Maximum repetitive peak reverse voltage, VRRM, and continuous reverse voltage, VR, according to the exact datasheet | Published reverse-voltage limits for the specified device | Nexperia 1N4148: VRRM = 100 V and VR = 100 V |
| Controlled-avalanche rectifier or TVS diode | Reverse breakdown voltage, VBR or V(BR) | Minimum or maximum reverse voltage measured at the specified reverse current | JEDEC JESD282B.01 section 5.6.7 specifies V(BR) for these device classes |
| Power rectifier | Maximum repetitive peak reverse voltage, VRRM | Maximum rated reverse peak that may recur without permanent damage | 1N4001: 50 V; 1N4007: 1000 V |
| Voltage regulator or Zener diode | Zener voltage, VZ | Working reverse voltage at the datasheet's stated Zener current | BZX84-A5V6: 5.54 V to 5.66 V at IZ = 5 mA |
The 1N4002 diode guide gives a practical rectifier example. Always check its manufacturer datasheet before selecting a replacement.
What Is Breakdown Voltage?
Breakdown begins at the knee of a reverse current-voltage curve. Below that region, only a small reverse current flows. At the knee, reverse current rises rapidly for a small change in voltage.
Do not treat every reverse-voltage term as another name for breakdown voltage. The symbols answer different design questions.
| Symbol | Parameter name | What the number describes | How datasheets use it |
|---|---|---|---|
| VBR or V(BR) | Reverse breakdown voltage | Voltage measured when a specified reverse current flows just beyond the knee | Electrical characteristic |
| PIV | Peak inverse voltage | Peak reverse stress across a diode in a rectifier circuit, or a vendor's reverse withstand label | Circuit stress or vendor-defined rating |
| VRRM | Maximum repetitive peak reverse voltage | Maximum reverse peak that may be applied repeatedly without permanent damage | Absolute maximum rating |
| VZ | Zener voltage | Regulating voltage measured at a stated Zener current and junction temperature | Operating characteristic for a Zener diode |
The JEDEC rectifier standard measures VBR at a specified reverse current. It tests VRRM separately as a repetitive no-damage rating. This distinction is why a designer should compare the circuit's peak inverse voltage with a published reverse-voltage rating, not with an assumed breakdown knee.
Parameter names also vary by manufacturer. ROHM uses VRM for the quantity that JEDEC and IEC call VRRM. Read the parameter name, symbol, conditions, and footnotes together.
How Diode Reverse Breakdown Works
Reverse bias connects the cathode toward the positive supply and the anode toward the negative supply. The depletion region widens, and only a small leakage current flows until the junction approaches breakdown.
For a conventional rectifier, the reverse-voltage rating is a blocking limit rather than an operating target. Uncontrolled breakdown current can overheat and destroy the junction. Select enough margin so normal peaks and repetitive switching transients remain within the datasheet rating.
The Vishay 1N400x datasheet illustrates the point. Its maximum repetitive peak reverse voltage table lists 50 V for the 1N4001 and 1000 V for the 1N4007. These are VRRM ratings, not claimed VBR test values.
The same table lists maximum root mean square voltage and maximum DC blocking voltage separately. Use the row that matches the waveform and duty in the circuit.
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How Doping and Temperature Affect Breakdown Voltage
There is no universal breakdown-voltage formula that gives a reliable value from the word "silicon." Junction doping sets the depletion width and electric field, while the datasheet test current and temperature define the reported value.
| Breakdown region | Junction condition | Typical voltage region | Temperature coefficient |
|---|---|---|---|
| Zener or field-emission breakdown | More heavily doped junction with a narrow depletion region | Dominant below about 5 V | Negative |
| Mixed region near 5.6 V | Zener and avalanche contributions overlap | About 5 V to 8 V; the onsemi HBD854/D handbook identifies 5.6 V as the common near-zero case | From negative through near zero to positive; depends on test current |
| Avalanche breakdown | More lightly doped junction with a wider depletion region | Dominant at higher breakdown voltages | Positive |
Heavier doping produces a narrower depletion region and a stronger electric field at a lower reverse voltage. Lighter doping produces a wider region, allowing carriers to gain energy and generate more carriers through collisions.
The approximately 5.6 V crossover is an important exception to simple labels. Both mechanisms contribute there. Nexperia specifies a temperature coefficient from -2.0 to +2.5 mV/K at 5 mA for its BZX84 5V6 selections, so the result can cross zero.
How to Read Zener Voltage
A Zener diode is intended to work in reverse breakdown with controlled current. Its datasheet therefore specifies Zener voltage, VZ, at a stated Zener current, IZ. VZ is not one exact voltage at every current and temperature.
For example, the Nexperia BZX84 series datasheet specifies the BZX84-A5V6 from 5.54 V to 5.66 V at 5 mA and 25 °C. Its B and C tolerance selections have wider ranges at the same test current.
A series resistor or another current-limiting element must keep the diode within its current, power, and temperature limits. The onsemi Zener handbook shows that Zener diodes normally operate inside the breakdown region, while external resistance absorbs excess voltage and limits current.
Avalanche vs Zener Breakdown
Avalanche breakdown and Zener breakdown are different physical mechanisms. In avalanche breakdown, carriers accelerate through a wider depletion region. Their collisions release more electron-hole pairs, producing carrier multiplication.
The mechanisms also move in opposite directions with temperature. Zener breakdown voltage decreases as junction temperature rises, giving a negative coefficient. Avalanche breakdown voltage increases, giving a positive coefficient. Around 5.6 V, their contributions can partly cancel.
The mechanism name does not replace the datasheet parameter. A commercial device called a Zener diode can operate through field emission, avalanche multiplication, or both. Read VZ, IZ, impedance, tolerance, power, and temperature data for the exact part.
How to Read the Right Voltage Rating
Start with the circuit requirement, then identify the matching datasheet field. Determine the peak inverse voltage in the circuit and compare it with the diode's repetitive and DC reverse ratings. Use VBR only with its stated test current.
For a Zener regulator, use VZ at the relevant current and temperature, then limit current and power. For an ordinary rectifier, do not plan to operate in breakdown.
A flyback diode is one application where reverse and transient ratings matter. The 2N2222 pinout and switching guide shows that diode in an inductive-load circuit.
Primary definitions and rating conventions are available in JEDEC JESD282B.01 and ROHM's diode ratings application note.
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