I think the next really big milestone (at least for me) was the day I built a simple small signal amplifier. It was a class A amplifier and I had to learn many things before I was ready to build one (one that worked!). When that day finally came (after I don't know how many failed attempts) I was so excited I could hardly contain myself. Who are we kidding, I didn't contain myself, it was too exciting!
Nowadays, when I need gain, I use op-amps almost exclusively. Very rarely do I use discrete transistors for amplifying signals anymore. Not that they don't have their place, it is just that most of the stuff I do an op-amp is a better fit. That being said, there are still situations, usually when going for the absolute lowest noise possible, when you still can't beat a physically large BJT or JFET transistor as your first stage of gain.
What is a Transistor?
A valve used to control water flow allows a small exertion of energy (a person turning it) to control the flow of a lot more energy (a lot of high pressure water).
What is a Class A amplifier?
Below is a Class A amplifier in all it's simplified glory!
Single Transistor Class A
BJT and JFET
A test like this is a lot like compare apples and oranges (both fruit, both transistors but that is where it ends) and so I tried to find parameters that would allow me to draw the best comparisons I could (not necessarily the way you might see them compared elsewhere). In the end, all of this testing was for my own purposes and is only presented here in case it can be enlightening, educational or otherwise useful by anyone else.
General properties of Bipolar Junction Transistors
Current controlled (simplified point of view)
Lowest input impedance
Voltage drop from Base to Emitter (about 0.7V)
Highest potential Gain
General properties of Junction Gate Field-Effect Transistor
High input impedance
Good temperature stability
Low noise (lower than MOSFET, not lower than BJT)