Reverse Leakage Current: Reading Microamps in the Data Sheet and on the Bench
Read diode leakage at the correct voltage and temperature, calculate standby drain, and identify meter burden, fixture leakage and resolution limits.
Reverse leakage current must be read with reverse voltage and junction temperature. A room-temperature limit does not establish the hot value, and there is no universal tenfold increase per 25 °C that can supply a missing curve. Use the selected diode’s data, then check whether the measurement setup can resolve the current you are budgeting.
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What the Data Sheet Means by IR at VR
IR is current under reverse bias at a stated voltage and temperature. Distinguish a maximum limit from a typical curve. Also check whether a value applies to one junction or a multi-diode assembly.
Voltage, temperature and the device structure affect the result. Do not carry a value measured at a lower voltage into a higher-voltage design without evidence. The rectifier parameter definitions from Vishay explain the rating terminology; they do not supply the leakage curve for an unidentified part.
Estimating Hot Leakage Without Inventing a Multiplier
Look for limits or curves at the required reverse voltage and temperature. If only typical data exists, keep that distinction in the design record. If hot leakage is critical and the needed information is absent, obtain it or measure under an agreed method rather than multiplying a room-temperature number by a generic factor.
For an explicitly assumed constant standby leakage of 300 µA, 30 days represents 720 hours, so charge consumed is 0.0003 A × 720 h = 0.216 Ah. At 30 µA it would be 0.0216 Ah. This example shows sensitivity of the battery budget; it does not assert that a 30 °C rise causes either current.
PN vs Schottky Leakage: Compare the Actual Parts
A silicon Schottky’s lower barrier can trade forward-drop savings against reverse leakage. The difference from a PN device depends on part, voltage and temperature. Neither a fixed hundredfold ratio nor a nanoamp claim follows from a catalog image.
At an assumed 40 V and 1 mA reverse current, reverse power is 0.040 W while that bias is applied. Multiply by the applicable blocking-time fraction for a cycle average where appropriate. Temperature feedback can make reverse loss important even when the forward-loss comparison looks favourable.
Measuring Leakage with a DMM or SMU
For a suitable isolated, current-limited low-voltage test, apply a known reverse voltage and measure current in series. Never place a current-range meter directly across a voltage source. Respect the meter’s voltage, current, protection and connection requirements; high-voltage leakage testing requires a designed fixture and qualified procedure.
Measure or account for the actual voltage across the diode because meter burden can change it. Record temperature, settling time, range and resolution. Remove parallel circuit paths when they would dominate the reading, and measure the clean empty fixture to identify its background leakage.
Keithley’s diode-production test note discusses stray leakage and guarding. If fixture current is comparable to the expected device current, a displayed number does not yet establish the diode’s leakage. An SMU or electrometer can be more suitable for very low currents.
When Leakage Becomes a System Problem
Use worst relevant operating conditions for standby drain, high-impedance sensing errors and reverse power. Temperature and reverse bias must match the task; ambient is not automatically junction temperature during powered operation.
A displayed zero means below the setup’s resolution, not zero leakage. A high reading can reflect contamination, humidity, a parallel path or device damage. Resolve the setup before diagnosing the junction. For the feedback problem, continue to the Schottky thermal-runaway analysis.
Frequently Asked Questions
Can I use a tenfold-per-25 °C rule for any diode?
No. Use the selected device’s voltage- and temperature-dependent data. A generic multiplier cannot establish a missing hot leakage limit.
Does zero on a microamp range mean no leakage?
No. The current may be below the range’s resolution or masked by the measurement setup.
Why measure the voltage across the diode as well as current?
Meter burden and series impedance can change the actual reverse bias. The reading needs the voltage and temperature conditions that produced it.
Can a large leakage reading prove the diode is damaged?
Not alone. First exclude fixture leakage, contamination, settling effects and parallel circuit paths.
Continue through this engineering topic
For the complete selection, design, verification, and troubleshooting path, explore the Rectifier Testing Failure and Reliability.
- Practical guide: Diode Test Mode: The Three Readings That Tell You Good, Open, or Shorted
- Practical guide: Soldering SMB and SOD-123 Packages: Reflow, Pads, and Inspection
- Practical guide: Thermal Cycling and Power Cycling: Predicting Rectifier Life
- Ask Good-Ark technical support about this application