I try to feed the EVAL-AD7357EDZ with a signal between 100KHz and a few MHz (with an estimated amplitude of micro volts) coming from a piezo-electric transducer of high impedance (more than 100MOhm). I suspect this fails because there is a significant impedance mismatch between the transducer and the ADC and because my signal is too low.
I am thinking to use a low noise preamplifier (something similar to AD797). Is there any evaluation board which has input impedance in the range of 10 MOhm to 1GOhm? Is there any possibility to modify one? (your lights please)