555 IC Oscillator with 50% Duty Cycle

A square wave oscillator using 555  IC can be configured to give symmetric oscillation (50% duty cycle). Other circuit uses diodes to split the charging and the discharging paths through different resistors, but here we need no such diodes. Here is the schematic diagram:


The time period for the output high is the same as regular configuration,
t1 = 0.693 RA C,
but for the output low, the period is
t2=[(RA.RB/(RA RB)].C.Ln[(RB-2RA)/(2RB-RA)]
Thus the oscillator frequency is? equal to 1/(t1 t2).
Please remember this oscillator circuit will not oscillate if RB is greater than 1/2 RA because the junction of RA and RB cannot bring pin 2 down to 1/3 VCC and trigger the lower comparator. [Circuit's schematic diagram source: hqew.net]