The circuit converts the input alternating signal into a direct current signal. If the input signal frequency is very low, the input capacitor C1 can be canceled. At negative half cycles, the output of op amp IS1 is connected through diode D1 (off-voltage is 0.7V) and is in-phase isolated via diode D2. The op amp IS2 operates as an inverting voltage follower. In the positive half cycle, IS1 operates as an inverting amplifier and is connected to the addition point via R2. At the input, resistor R3 and resistor R2 form a negative feedback loop. Z18 Bone Conduction Headphones Z18 Bone Conduction Headphones,Bone Conduction Headphones Gaming,Wireless Sports Headset,Outdoor Sports Bone Conducting Headset Shenzhen Lonfine Innovation Technology Co., Ltd , https://www.lonfinesmart.com