I'm sorry, this didn't come across very clearly in the webcast. At the time I was talking about a hypothetical circuit with a single gain stage, but at any given gain stage in a circuit, you can simplify in in this way. I refer to the "input noise sources," eni, as the combination of all of the noise sources before the gain stage, and the "output noise sources," eno, as the combination of all the noise sources after the gain stage. Thinking about it this way makes it simpler to think about the effect of taking more or less gain.
