Homework on Transistors (solutions)

Feel free to work on the homework in groups. The work you hand in, however, should reflect your understanding of the material and be in your own words.  Students who turn in identical (or close to identical) homework assignments will be asked to explain their answers orally to the TA or prof.  A student who cannot explain how he or she arrived at a given answer will be charged with academic dishonesty.

You should  justify all of your answers for full credit.

1. Explain why the first transistors made commercially were bipolar  junction transistors and not field effect transistors.  Why were field effect transistors more difficult to make even though they appear simplier (in principal) to make?
Field effect transistors require the technology to make surfaces with almost no defects. BJTs are significantly more fault-tolerant.

2.  If the current amplication (beta) of a npn bipolar junction transistor is 150, what fraction of the electrons coming out of the emmitter will make it all the way across the base and into the collector?  You can get additional help on this question from the web site http://hyperphysics.phy-astr.gsu.edu/hbase/solids/trans.html#c1
The current amplification of 150 means that the number of electrons making it all the way across is 150 times the number that get caught in the base. Thus, 150/151, or 99.34%, of the total number of electrons make it all the way across the base.