PNP Transistor Gain Higher than NPN?

anybody know w hy the PNP compliments always measure higher hfe than NPN?

we see this on a regular basis

using 500 ma I-c and 4 V-dc to test,  maybe we need to use a higher current?

thanks!

I think this was true in germanium transistors for some physical reason that it was easier to make PNP transistors higher gain with less noise. No idea about silicon, though.

CJ said:

anybody know w hy the PNP compliments always measure higher hfe than NPN?

Click to expand...

I am not sure why, but these are more than two sides of the same coin. If you turn a PN junction upside down it does not alternate but  becomes reverse biased. One is doped with excess holes, the other excess electrons (you can look up which if it matters.)

we see this on a regular basis

Click to expand...

Yup.. I suspect when complements are set up they normalize for some other factor and the beta lands where it does.

Back in the 70s when I discovered some very low noise complementary devices, the PNPs were slightly lower noise and coincidentally higher beta (equivalent input current noise is influenced by current gain.)

using 500 ma I-c and 4 V-dc to test,  maybe we need to use a higher current?

thanks!

Click to expand...

I suspect this just is the state of solid state... or in other words I do not know the answer to your question.

In the early days of solid state power amplifiers robust NPN power transistors were more available. Complementary power PNPs were made by cobbling together a darlington pair with small PNP driver in front of a larger power NPN. It worked after a fashion but there were compromises due to asymmetry (slower due to larger turn on/off delay requiring extra stability compensation.) 

JR

Hfe changes significantly with temperature an Ib-Ic in high power transistors, so the SOA limits are more relevant, IMO.

CJ said:

using 500 ma I-c and 4 V-dc to test,  maybe we need to use a higher current?

Click to expand...

Hi CJ,
what method/device did you use to measure the Beat at 500ma of collector current?

500mA seems already high enough

> In the early days of solid state power amplifiers robust NPN power transistors were more available.

In the earlier, Germanium, days, only PNP was practical above a part-watt. I was recently reminded when I saw a stereo console plan with negative hot. Oddly, the preamp was PNP Silicon (which at that time cost a penny more than NPN-Si). But then the power amp was revealed as a all-Ge all-PNP with transformer drive.