TI recommends to drive transducers with a sine or square wave at the center frequency to achieve the best results. Most integrated designs have an output driver consisting of low-side drivers to drive a transformer in a transformer-drive situation, or FETs in an h-bridge configuration for a direct drive design. After the transducer sends out an echo at the resonant frequency, the system must then listen for return echoes which are a result of an object in the transducer's field of view. Ultrasonic systems typically filter the return echo to remove noise and gain the signal up before going to an ADC. Some ways to gain the ultrasonic system are as follows.