It works!

For 6.776 (the RF CMOS class I am taking) we have a lab assignment to work in pairs to make an amplifier centered at 50 MHz with a gain of 25 and an input impedance of 50 ohms along with several other specs. Figuring out the design and getting it to work in the simulator took some work but nothing too bad. But when it comes time to build something that works at 50 MHz things you might never think of all of a sudden make a big difference. Such as the scope probe we use to measure signals is actually the load of the amplifier since 10 pF is rather significant at 50 MHz. So you cannot look at the voltage at any point in the circuit other than the output because attaching the scope probe significantly changes the circuit.
Luckily it is at 50 MHz and not 100 MHz since that is where all of the FM stations are, but even at 50 MHz you have to contend with all that junk being transmitted when taking measurements.
Anyway, when we started building it we were having a really hard time getting any gain and it seemed like we had maxed out at about 6. For some reason I let myself feel all defeated and thought we would never get it to work. The entire time Susanna told me that we would figure it out and that once we did I would go on and on about how much I love building circuits and how glad I would be that we had to actually build it and not just simulate it.
Well it eventually struck me that we could get more gain by adding a buffer stage after our amplifier (for low frequency stuff that would be obvious, but for RF there are reasons why it is not). So my partner and I went in and rebuilt it, but we didn't have all the right values of parts and for some reason the TA thought that grad students don't have to be in their office on Sundays so we got to a gain of 11 and things were looking up.
Today we got the inductor values we needed and rebuilt it and then started switching around values of various components somewhat at random to see what would increase the gain. Eventually we got to a gain of about 24.5 at which point we tried things like jiggling components and blowing on it so no avail. Eventually I adjusted the variable capacitors a bit more and decided that my partner was being a bit stingy with his measurement on the scope and we called it a success with a gain of exactly 25 at exactly the output swing we needed. Tomorrow we find out if our TA agrees. And of course on the walk home today I thought about how much I love building circuits and how glad I am that we did not just simulate it.

Why did you just read all of that? Well I can't sleep and I don't feel like working on my thesis right now and hence another blog entry is created...