Astable multivibrator...without diodes...
Variation in upper resistance...variate high time....but variation in lower resistance ..variate in both high and low time.....
T..high=0.693(R1+R2)
T...low=0.693(R2)
Time period=0.693(R1+R2)+0.693(R2)
=0.693(R1+2R2)
Thank u...................
