Hi, for my integration class I am building a scanning tunnelling microscope (STM). I found some interesting designs and I choose the cheapest one (students are poor) witch uses a unimorph disk. The circuits are not that hard to build but I also need to understand them. I have some knowledge in electronics but not enough to understand every aspect of the electronics involved. Here are the circuits (sorry pdf): http://www.geocities.com/spm_stm/Simple_STM_Rev_C.PDF" The circuits are mostly composed op-amp's wich i understand basicly but not enough to understand these circuits. So here are my questions: What are the effects of using a capacitor coupled with an op-amp (only used them basically with resistors)? On op-amp in D1-D2 what is connected to 1 and 5 and what is the use of 1-5? What are the TP (TP1,2,5,6)? Instead of using and BNC male connector output for the oscilloscope is it possible to use an audio like male connector and plug it into a computer sound card (analog2digital) and use a software oscilloscope? What are the uses of the potentiometers and how do they work? Can the circuits be improved? If you have any other suggestions don't be shy, I am opened to anything. Also don't be scared of being too technical, I will figure it out or read around to understand it. Thank you in advance. P.S. I will also post in the engineering design section and in quantum physics one for other questions. So if you are interested about other part or have a lot of knowledge on STM's you can go to the two other threads. https://www.physicsforums.com/showthread.php?t=109369" https://www.physicsforums.com/showthread.php?t=109377"