Hi I am designing a ultrasonic range finder. I am part of design group with the challenge of building a robot that can find its way through a known course. I found some circuits avaliable on the net. There is a section on the transmitter circuitry that confuses me. I am using microcontroller to generate a 0 - 5V 40KHz burst of pulses. I want to boost the signal to have a larger voltage swing, and current drive to achieve larger power transmission hence further distance. I can amplify the voltage to 0 - 9V, but now how do I achieve a -9V to 9V swing? The circuit uses hex inverters. Doesn't a hex inverter represent a logic 0 as ground? The explanation given about why two hex inverters are in parallel is still not clear to me. I am using a PIC microcontroller, which drives out about 20mA. I want to achieve the max power transmission for a 40KHz piezo transducer. For current amplification, how does one design a current amplify for a -9V to 9V signal?