(5)工作波形与振荡频率计算 tpL=R2C1n2≈0.7R2C tpH=(R1+R2)CIn2=0.7(R+R2)C f21 1.43 IpL +ipu (R+2R)C Vcc R 8 4 3 1 555 (5)工作波形与振荡频率计算 tPL=R2C1n2≈0.7R2C tpH = (R1+R2 )C1n2≈0.7(R1+R2 )C PL PH 1 2 1 1.43 ( 2 ) f t t R R C =  + + VCC vC v O C 0.01F 8 4 555 7 6 2 3 5 1 R1 R2 vC VCC 2 3 VCC 1 3 O vO O tPL tPH t t