Hi guys,I'm looking for a tutorial on the long tailed pair differential amplifier topology for transistors, BJT or FET. All I can find by googling is opamps as differential amplifiers or valves as long tailed pair phase inverters.Specifically what I wanted to do is make a single-ended non-inverting amplifier with negative feedback into the inverting input, just like a very simple op amp in a standard non-inverting amplifier topology but from discrete parts. I'm aware that going to discrete parts instead of using opamps is rarely a good thing, but this is more for educational purposes than trying to achieve some advantage over an opamp.I've made a simple BJT spice model, with a voltage buffer before the feedback, but it doesn't seem to work the same as an opamp. It does amplify, but the input headroom is tiny regardless of feedback factor and the inverting and non-inverting inputs seem not to be tightly coupled together as one would expect from a negative feedback opamp.I only put this together from the knowledge that it works as a common collector coupled to a common base by their emitters, so any guidance on biasing etc would be helpful, and if there's a website that explains this well, that's be great. It doesn't have to be specifically to do with audio amplifiers.Cheers,Matt