Jonathan Ward

For my senior project during my last semester in college, I designed a Low Noise Amplifer for use in MRI systems. When I started the project, it was supposed to be used in an MRI research system. The researcher wanted an onboard LNA for his sense coils. I created an LNA with 13 dB of gain and 1 MHz of bandwidth centered at the Lamor Frequency for his system of 64 MHz. Halfway through the project, I was told that he had obtained some commercial amplifiers that met his specifications and that my work was no longer necessary. Undeterred, I pressed on with my work.

I came up with an amplifier design that was able to achieve his specs. My college didn't have any equipment to measure noise figure, so I wasn't able to measure the low noise aspects of the amplifier. I used a low noise BJT with a theoretical mimimum NF of around 1.2 dB. I really wish I had access to the right equipment, but my school didn't do much RF research. What little RF research they had was focused on wireless sensing applications and low noise was not a primary concern.

After many iterations, here is a picture of my final design: