There are mainly two ways in which an ultrasonic transducer can be driven. The first one is the Transformer drive and second is direct drive and which type to choose mainly depends on the voltage requirement for exciting the transducer.

Transformer drive as the name suggest uses a step-up transformer to drive the transducer. The primary coil of the transformer is excited with low voltage signal and secondary side (which has a much higher voltage swing) drives the transducer. With transformer drive one can achieve the transducer excitation voltage beyond 100Vpp and so are generally preferred where the sound pressure level requirement is high like for application which requires measuring or detecting object at large distances.

Direct drive uses a H bridge (full or half) driver or an amplifier to directly drive the transducer. So in this the maximum excitation voltage is limited to the power supply of the system. These are mainly used for application where we don’t need large sound pressure level.

Type of mode to select also depends on the construction type of the transducer. Many open-top transducers do not require more than tens of volts to generate the maximum transmittable sound pressure level (SPL), so a transformer is not necessary, and a direct-driver mode is recommended. Closed-top transducers can also be excited in the direct-drive mode, but the transducers effective range is limited due to the typical requirement of hundreds of volts to generate the maximum transmittable SPL.