The performance of thin-disk transducers made of PZT-5A ceramic using acoustic matching and air-backing is described using simplified 1-D model and experimental results. Several ultrasound transducers have been designed for studying influence of high power ultrasound energy on tissue. PZT-5A ceramic has been used as active element with thickness approximately lambda/2, depending on working frequency (500 kHz, 1 MHz, 2 MHz) and with three different diameter to thickness ratio (D/t) for obtaining different directivity patterns in radiated medium. Theoretical input impedance, conductance and bandwidth of transducer systems has been compared with experimental results. Theoretical results have been derived using Mason's equivalent circuit