555 Astable Multivibrator

T=0.69RC=0.69 (Ra+2Rb)C 8 and 4 shorted=> No reset 2 and 6 shorted Capacitor C from 6 to ground Ra is connected b/w 8 and 7 Rb is connected b/w 7 and 6 5 capacitor grounded to reduce tipples in dc supply (5V => Vcc) 3 is output Capacitor charges via Ra and Rb but discharges through Rb only. So charging cycle T1=0.69 (Ra+Rb) C Discharging cycle T2= 0.69 Rb C TIME PERIOD=T= T1+T2= 0.69 (Ra+2Rb)C Observe that capacitor charges and discharges between (1/3) Vcc and (2/3) Vcc Ra=1k, Rb=10k, c=0.1uF; T=1.449mS f= 690Hz Ra=10k, Rb=22k, c=0.1uF; T= f= Ra=500, Rb=1k, c=0.1uF; T=172.5uS f=5.79KHz

published 10 years ago