Most of the time, we need to coil voltage and current reaches the maximum value, so as to generate a maximum alternating electromagnetic field, then they would have the same power amplifier frequency selection circuit resonant frequency and the frequency of the exciting signal, power amplifier will resonate. In the online world, there is a very close friend: the wireless charging coil and the wireless charging coil, which often appear on the screen. One recent discovery is that when the wireless charging coil and the wireless charging coil are close, the sensing voltage is generated when the resonant frequency of the wireless charging coil circuit is the same as that of the transmitting frequency. In fact, the wireless charging coil circuit and the wireless charging coil loop are in the resonant state, with the best energy transmission effect. In fact, two of them can also be individually to perform tasks, so in our eyes, they are a very flexible guy.