What electrical characteristics are specified in the diode technical datasheets?

The main electrical characteristics specified in the diode datasheet are forward voltage, reverse current, terminal capacitance, reverse recovery time, etc.

This section describes each of the electrical characteristics specified in diode datasheets. Different electrical characteristics may be specified for different types of diodes. Electrical characteristics are specified at an ambient temperature (Ta) of 25°C unless otherwise noted.

An example of an electrical characteristic item in a diode technical datasheet is shown below.

Characteristic Symbol Test Condition Min Typ. Max Unit
Forward voltage VF (1) IF = 1 mA 0.61 V
VF (2) IF = 10 mA 0.74
VF (3) IF = 100 mA 0.92 1.20
Reverse current IR (1) VR = 30 V 0.1 µA
IR (2) VR = 80 V 0.5
Total capacitance CT VR = 0 V, f = 1 MHz 2.2 4.0 pF
Reverse recovery time trr IF = 10 mA (Fig. 1) 1.6 4.0 ns
  • Forward voltage (VF) / peak forward voltage (VFM)
    VF and VFM are voltage drop that occur across a diode’s terminals when electric current flows in the forward direction under the specified current and temperature conditions. This is called forward voltage VF. Since VF and VFM are highly dependent on temperature, they are specified under a pulsed current condition for some diodes. In this case we call it the peak forward voltage VFM.
    Generally, silicon SBDs have a negative temperature coefficient whereas SiC SBDs have a positive temperature coefficient in the high-current region. Therefore, parallel connection of Si diodes is not recommended due to the risk of thermal runaway.
    The following FAQ has an explanation about temperature characteristics. please refer.
    FAQ:How does heat change the characteristics of a diode? (Temperature Characteristic)
I<sub>F</sub> – V<sub>F</sub> Curves
IF – VF Curves
I<sub>R</sub> – V<sub>R</sub> curves
IR – VR curves
  • Reverse current (IR) / repetitive peak reverse current (IRRM)
    IR and IRRM are the leakage currents that flow in the reverse direction when a diode is reverse-biased at the specified voltage. Since the leakage currents are highly dependent on temperature, they are specified under a pulsed current condition for some diodes. Note that IR and IRRM are different from the maximum reverse recovery current observed during the reverse recovery process.
C<sub>j</sub> – V<sub>R</sub> curve
Cj – VR curve
  • Junction capacitance (Cj) / total capacitance (CT)
    The main capacitance is the capacitance generated at the junction. There is a depletion layer at the junction, and there are almost no carriers (electrons or holes). This part corresponds to the insulation band of the capacitor. Since the width of the depletion layer is related to the magnitude of the applied reverse bias VR, the junction capacitance is inversely related to VR.
    In the datasheet, Cj and CT are defined as the equivalent capacitance between the terminals when a small signal with the specified frequency is applied under the specified reverse voltage condition.
Diode turn-off operation (Reverse recovery time)
Diode turn-off operation (Reverse recovery time)
  • Reverse recovery time (trr)
    It takes some time to bring a forward-conducting diode into a non-conducting state by applying a reverse voltage. When forward voltage is applied across a pn junction diode, electrons are injected into the n-type semiconductor (i.e., cathode side) while holes are injected into the p-type semiconductor (i.e., anode side). These majority carriers recombine near the junction or diffuse across the junction as minority carriers, causing electric current to flow.
    When reverse voltage is applied, negative current (i.e., reverse recovery current, irr) flows first, canceling out these majority carriers. Some of the minority carriers remaining in each layer recombine and disappear after a certain period of time (lifetime) has passed.
    Reverse recovery time (trr) is the time required for reverse recovery current (irr) to disappear. In datasheets, trr is specified as follows. Forward current (IF) and its falling slew rate (di/dt) after the application of reverse voltage (VR) are specified as test conditions. Let the time required for IF to reach the peak value of the reverse recovery current (irr) value from the zero-crossing point be t1. Let the time required from the peak irr value to the zero-crossing point of the line passing through the 90% and 50% points of irr be t2. Then, reverse recovery time (trr) is defined as the sum of t1 and t2.
Diode turn-on operation (Forward recovery time)
Diode turn-on operation (Forward recovery time)
  • Forward recovery time (tfr)
    When a rapidly rising forward volta Even if a rapidly rising forward voltage is applied, the diode does not immediately become conductive. It takes a little time for enough carriers to be accumulated before the diode obtains high conductivity. Although the diode is forward-biased, it exhibits high resistance during this period and therefore a higher voltage than the VF value in the conducting state. This phenomenon is called forward recovery. A diode consumes more power during the forward recovery period than it does in the steady state.
    In datasheets, tfr is defined as the time required for forward voltage to reach its peak from 10% of VF and then drop to 110% of VF at the specified forward current (IF). High-voltage diodes tend to have a long forward recovery time.

In addition, some diodes have individual maximum ratings. See the application note below for details.

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