555 8-pin integrated circuit diagram

Pin 8 of 555 is the operating voltage input terminal of the integrated circuit. The voltage is 5~18V, expressed in UCC. From the voltage divider, it can be seen that pin 5 of A1, pin 6 of the upper comparator, is connected between R1 and R2, so pin 5 The voltage of A2 is fixed at 2UCC/3; the lower comparator A2 is connected between R2 and R3, and the potential of the non-inverting input terminal of A2 is fixed at UCC/3.