Rbe comparison

Below I listed up a few values of rBE or Rbulk which I measured for various dual and single transistors. The procedure is to measure Vce (collector is open) while variing the base current from a few hundered micro amps to about 5 miliamps. I used a set of a few fixed resistors in the range from 1k to 15k for the base current. The Rbe is the high current slope of the Vce vs Ib graph. As we see the PNPs have generally poorer performance than their complementary counterparts. This is due to the different carrier mobility in p-Si. Also one can see the very poor performance of the CA3046. The figures suggest that one maybe gets away with single transistors glued together. At least for less critical applications. Finally I measured the difference in Vbe for the arrays (fixed base current of about 100 microamps), the collector was open. I found that all of the pairs were within one millivolt.

Why is the value for Rbe interesting? One effect of Rbe is that it delimits the gain of a single transistor stage. And in the context of synthesizer circuits it affects the accuracy of an exponential converter. It is usually not given in datasheets.