Amplifier and Transducer coil.
EMAT amplifier is based on AD830 IC and a cascode amplifier. I've taken the schematic from this article . I also added a LC oscillator to measure the inductance of coils. The inductance of transducer coil is less than 1 uH and I don't have a LC meter capable to measure such a small value. Instead the oscillator frequency could be measured. The formula to calculate the LC oscillator frequency is the following: Where In my case CX1=47nF and CX2=10nF. A transducer coil has 10 turns of 0.16 mm wire glued with epoxy resin to 3D printed handle. After connecting to the LC oscillator it runs on frequency 1.83MHz. According to the given formula the coil inductance L is 0.91uH. Here is an assembled amplifier PCB with transducer coil attached to the LC oscillator. One can see three resistors placed on separate small PCB. These are R1, R2 and R3 resistors which should have had 2512 footprint (because they dissipate 1 W each) but I made a mistake and selected the default