Low power continuous wave ultrasound transmitter

A system and method for providing a continuous wave ("CW") ultrasonic drive signal and a B-mode ultrasonic drive signal from an ultrasonic transmitter are disclosed herein. An ultrasonic transmitter includes a first shunt transistor and a second shunt transistor. The first shunt transistor shunts positive transmitter output voltage to ground. The second shunt transistor shunts negative transmitter output voltage to ground. The shunt transistors include control inputs that, when modulated, cause the shunt transistors to produce a CW ultrasonic drive signal on a transmitter output. The ultrasonic transmitter also includes a first CW control transistor coupled to the first shunt transistor, and a second CW control transistor coupled to the second shunt transistor. The first and second CW control transistors respectively provide negative and positive CW drive voltage to the first and second shunt transistors.