I'm designing a general purpose ultrasonic modulator. Long ago, I built one from McGraw Hills Circuit encyclopedia, using a 555 chip. It generates an square wave carrier, and by feeding pin #5 produce PWM, and thus can Mo/Dem light to sound, though it's output is limited, plus square waves are not too pleasant to listen to. Is there any updated chip option, sine wave, with filter capabilities, and beyond 100khz? Can I get a diagram?