Step excitation source for ultrasonic pulse transducers

A circuit is described for exciting ultrasonic transducers by step discharge through avalanching transistors. While a free-running mode is possible, the circuit is designed for synchronous operation at 1 and 10 kHz repetition rates. During the receive mode the transducer is decoupled from the power source. The output is obtained from a buffer amplifier to match a 50 Ω coaxial cable. The circuit described produces a 250 V step discharge into a 24 pf load in 10 ns.