Doubt regarding astable multivibrator

[audioguru]

If you design a circuit using "typical" values then some of the weakest but passing devices will not work.
But if you design using minimum values then ALL passing devices will work perfectly.

ALL my designs work perfectly. Guess why?

Note that an opamp is overloaded if its load (or negative feedback) is less than 2k ohms.

 

[Raj89]

Mr. grossel, i do know that this circuit works as a partial shmitt trigger. when the product of the open loop gain and β is large in a schmitt trigger, the output is not related to input in a linear manner, but instead shows two states of +Vss and -Vss. Also, the positive feedback gives a hysteresis. and when the differential input is< 0, the output remains at +Vss and when the capacitor here which replaces the external power supply in a schmitt trigger charges to β.Vss(voltage equal to that supplied in the positive terminal of the opamp), the differential output becomes 0 and the output shifts to - Vss. Hence, the capacitor's charging and discharging causesthe circuit's output to oscillate between + and - Vss and it behaves as an astable multivibrator. I hope i am right.

 

[siddharth.gits]

astbl multvbtr

i have tried all ways but coulldnt find a good solution.there 50 -60 combinations possible.for each resistor several values of capacitor are possible and vice versa.....

 

[audioguru]

The frequency of the very simple opamp oscillator changes when the supply voltage changes and also when temperature changes the values of the resistors and capacitor. You can add a trimpot in series with one resistor to adjust the frequency to what you want.