I'm not asking the definition, but wondering how do the manufacturers measure this parameter's quantity in a lab for instance? For example for Ic Vce characteristics they keep Ib constant and they obtain plots. What is the procedure for obtaining reverse saturation current of a BJT?


enter image description here

Ies in this case is Is: Reverse Saturation Current. When they measure it, they just take several different current readings for several different Base Emitter voltages. They also do this at a "constant" temperature, or they use a cold junction reference to actively measure the temperature. Solve for the unknown. (Note: "Ies" = emitter saturation current, and this is a first order approximation) You could put the base-emitter into reverse bias, but you'd need to be very careful to not destroy the device as Vebo is generally around 5V or less! Where as the first technique has much more tolerance for not destroying your BJT that you might want to use.

Edit: A more precise answer due to some ambiguity of the question.

enter image description here enter image description here enter image description here


  • ic = collector current
  • ib = base current
  • ie = emitter current
  • βF = forward common-emitter current gain
  • βR = reverse common-emitter current gain
  • Is = reverse saturation current
  • Vbe = base-emitter voltage
  • Vbc = base-collector voltage
  • Vt = thermal voltage

Solve for as many of these as you feel like to find Is.

  • \$\begingroup\$ Are you sure? Reverse Saturation Current flows from collector to base as far as I know. Emitter even can be open. \$\endgroup\$ – user16307 Jan 6 '16 at 18:41
  • \$\begingroup\$ @user16307, BJTs are a three terminal device. That means there are TWO reverse saturation currents. One for the Emitter and one for the Collector. The more useful is the emitter-base reverse saturation current, as that's the one that helps you determine emitter current versus base-emitter voltage in forward active and edge of saturation (where most bjts tend to be used). I'll edit the question to have the full equations. \$\endgroup\$ – Dave Jan 6 '16 at 22:46
  • \$\begingroup\$ no in all literature Reverse Saturation Current described as which flows from collector to base as leakage. please show a reference what u claim. \$\endgroup\$ – user16307 Jan 7 '16 at 6:15
  • \$\begingroup\$ You could think about it logically before asking for a source. If Is was the Reverse Saturation Current of the Base-Collector then no matter how much you increased the reverse biased voltage on the B-C junction, no more current would flow. That means that the only other source for current to the emitter would have to be the base. Thus with a reverse saturated B-C region delivering a "set in stone" current, as the emitter current rises, the base would have to provide ALL that increase. But that isn't the case. \$\endgroup\$ – Dave Jan 7 '16 at 11:07
  • \$\begingroup\$ @user16307, I highly doubt you've read "all literature" or you wouldn't be asking this question nor having this argument about why you think my answer is wrong. If you still insist on a source to prove my point: Solid State Devices 6th ed. page 357 (my old college textbook for my Solid State class) \$\endgroup\$ – Dave Jan 7 '16 at 11:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.