Linearity of the Transistor Amplifier

[ve3wwg]

I came across this great article from Wireless World May 1972.  The link for that article is here:

http://schematicsforfree.com/archive/file/Analog/Linearity%20of%20the%20Transistor%20Amplifier.pdf

I was interested in this because of what I had read in a recently purchased used book titled: "Principles of Transistor Circuits" by Stan Amos and Mike James.  This is a good summary of transistor parameters, which is great if you've become familiar with it in more detail with other texts first.

The issue concerned me since I am designing a solid state guitar amplifier. The author in chapter 7 "Small Signal A.F. Amplifiers" had dropped this little bomb about a case where the next stage would operate very non-linear, due to an inappropriate level of source resistance. This was something I had not given a lot of consideration to.

So I thought this would make a good LTspice experiment to prove the issue. So you'll find that documented here:

http://www.experimentalistsanonymous.com/ve3wwg/doku.php?id=ce_linearity

The original article above and the LTspice experiment confirms however, that unless you avoid negative feedback- you don't have much to worry about in this regard.

This also debunks another tube vs solid-state myth about the differences between these in their amplification of the signals (ignoring intentional tube overdrive). Both technologies use negative feedback and similarly achieve linear amplification. In the linear region, there is mighty little difference between them.