I'm trying to calculate the peak reverse recovery current \$I_{RM(REC)}\$ of a diode from information given on a typical diode datasheet (really what I want is the transit time TT, but the only piece I'm missing is \$I_{RM(REC)}\$).

A few sample datasheets for the 1N4148:

  • MCC semi: \$I_F = 50mA\$, \$I_{rr} = 0.1 I_r\$, \$R_L = 100 \Omega\$
  • Fairchild: \$I_F = 10mA\$, \$I_{rr} = 1mA\$, \$R_L = 100 \Omega\$, \$V_R = 6V (600mA)\$
  • Diodes INC: \$I_F = I_R = 10mA\$, \$I_{rr} = 0.1 I_R\$, \$R_L = 100\Omega\$

Relevant equation: \begin{equation} Q_{rr} = I_F TT = \frac{1}{2} t_{rr} I_{RM(REC)} \end{equation} Or, \begin{equation} TT = \frac{t_{rr} I_{RM(REC)}}{2 I_F} \end{equation} Additionally, typically \$t_{rr}\$ is measured until the reverse current has dropped to \$I_{RM(REC)}/10\$ (JEDEC JESD282B01, though it seems sometimes perhaps different ratio might be used?).

LTSPICE lists the 1N4148 as having TT=20ns, so this is the figure I am aiming for. All the datasheets list \$t_{rr} = 4ns\$. That means the ratio of \$I_{RM(REC)}/I_F\$ I am looking for is 10 (non soft reverse recovery diodes).

MCC semi

Because \$I_F = 50mA\$, somehow I need to find \$I_{RM(REC)} = 500mA\$. The only other \$I_R\$ is for large reverse voltages, and is on the order of nA/\$\mu A\$'s. I don't know what the relation between \$I_{rr}\$ and \$I_{RM(REC)}\$ is.


Because \$I_F = 10mA\$, somehow I need to find \$I_{RM(REC)} = 100mA\$. I don't know what the relation between \$I_{rr}\$ and \$I_{RM(REC)}\$ is.

Diodes INC

Because \$I_F = 10mA\$, somehow I need to find \$I_{RM(REC)} = 100mA\$. Again, I don't know what the relation between \$I_{rr}\$ and \$I_{RM(REC)}\$ is.

How do I find \$I_{RM(REC)}\$ for these three example datasheets? Or is there not enough information given? If there isn't enough information, is there any other way to get an estimate on TT (what I'm really interested in) from the info in the datasheets?

  • \$\begingroup\$ I'm guessing it's changes between devices and you'll have to measure it. (There's a nice app note by J Williams about charge storage in diodes.) \$\endgroup\$ Nov 14, 2014 at 3:05

1 Answer 1


There are different SPICE parameters..

For example, the NXP model has TT = 3.48E-9

Central Semiconductor has TT = 2.88E-9

Vishay 1N4148W (T154D chip) has TT = 4E-9

None of those looks much like 20ns, but I didn't look at every maker of 1N4148s.

In any case, you may find this Matlab page useful.

Datasheets do not typically provide values for TT and τ. Therefore the Diode block provides an alternative parameterization in terms of Peak reverse current, Irrm and Reverse recovery time, trr. Equivalent values for TT and τ are calculated from these values, plus information on the initial forward current and rate of change of current used in the test circuit when measuring Irrm and trr.

  • 1
    \$\begingroup\$ I pulled the 20ns figure looking at LTSPICE's model (which says it's OnSemi, but I can't find any datasheet from OnSemi for this part). I did come across the Matlab page (and a few others) which is where I got the simple equation for TT, though it looks like I'm not too wrong using \$I_{RR}\$ as the peak current as long as I don't expect too much accuracy (it's going to depend on a lot of other factors, anyways). \$\endgroup\$ Nov 14, 2014 at 4:10
  • \$\begingroup\$ I'm using the same diode from MCC Semi and trying to do this in MATLAB/Simulink. The "alternative parameterization" described is the closest I can get to full characterization - except I don't have the "rate of change of current used in the test circuit" - I don't see that on the data sheet and don't have the other info in these equations to calculate it. Does anyone know this or at least have a typical time used? \$\endgroup\$
    – Trashman
    Oct 17, 2022 at 21:07

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