Function of RC circuit in a bistable multivibrator using op-amp
The purpose of R-C circuit in bistable multivibrator, based upon an op-amp, is to create the pulse input to the op-amp to make it switch between the positive and negative saturation voltages of the operational amplifier operating with the given supply voltages.


  


The capacitor let's through (i.e. charges upon) the edge of the input signal and then decays through R1 thereby providing the pulse required.

A positive pulse switches the op-amp to its negative saturation, whereas a negative pulse swithes the op-amp to its positive saturation.


  




Source: Op Amp Bistable Multivibrator Circuit Design