超声波测距电路图。至于为什么接收不用晶体管做放大电路呢，因为放大倍数搞不好，CX20106集成放大电路，还带自动电平增益控制，放大倍数为76dB，中心频率是38k到40k，刚好是超声波传感器的谐振频率，感觉很合适。-Ultrasonic Distance Measurement circuit. As for why the receiver do not have to do the transistor amplifier circuit, because magnification well, CX20106 integrated amplifier, but also with automatic level gain control, magnification to 76dB, the center frequency is 38k to 40k, is exactly the resonant frequency of ultrasonic sensors, feel is appropriate.