http://en.wikipedia.org/wiki/Electronic_amplifier

http://www.st-andrews.ac.uk/~jcgl/Scots_Guide/audio/part2/page2.html

http://physgrad6.wustl.edu/321/Docs/Notes/SMH/PushPullAmp.pdf

http://www.electronics-tutorials.ws/amplifier/amp_6.html

http://www.eee.bham.ac.uk/collinst/ee3b1/slides/PowerAmps5.ppt

http://www.allaboutcircuits.com/worksheets/bjtamp_b.html

http://www.electronics-tutorials.ws/amplifier/amp_7.html

http://users.ece.gatech.edu/pallen/Academic/ECE_6412/Spring_2003/L060-Push-Pull(2UP).pdf

http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-776-high-speed-communication-circuits-spring-2005/lecture-notes/lec18.pdf

http://www.rose-hulman.edu/~herniter/Rose_Classes/ECE351/Notes/notes.htm