I'll try to keep this short because I don't want to muddy it up with a bunch of irrelevant details. I'll add more details as necessary. I have been messing with tube circuits for a little while and wanted a primer in transistors. I need a transistor for a switching circuit I'm working on, but as part of the educational initiative I've set out to build a small amplifier circuit. All I want to do is build a simple emitter follower amplifier, inject a test signal, and see it working on my oscilloscope. So far I have been unable to do that. I am surely missing something incredibly fundamental. Keep in mind the trouble may be with how I'm setting up the test or analyzing my results, not the circuit itself. I just don't know. I've looked at a bunch of different basic amplifier circuits but most recently built this one: For Q I am using BC108, I've also experimented with an MSPA13. For the power supply, I've tried a 9V battery as well as a 9V AC adapter. I get different results. Mostly the output sine wave has a bunch of noise on it, it's not clean and I don't know what to make of it. When using the 9V adapter I can generate what appears to be 120Hz wave greatly amplified, with my test signal superimposed (but presumably not amplified). When I use the 9V battery I just get some noise back of no significant increase in amplitude over the test signal. I feel like cleaning up all the noise I'm getting on my scope is one objective here. I can generate a clean sine wave on the scope using the test signal, so the signal, probes, and scope are all OK. It's when voltage is applied, or the signal passes thru the transistor, is when noise is being generated or collected. Let me leave it at that before I ramble on too long. Anything obvious going on here? What questions do I need to answer in order to move forward? Thanks in advance.