Transition from Sinusoidal to Relaxation Oscillations in Emitter-Coupled Multivibrators

Method of quasilinear approximation is applied to investigate the sinusoidal oscillations obtained in emitter-coupled multivibrators. The amplitude and frequency are found, and frequency decreasing occurring in development of oscillation from the starting point to steady state is explained. The transition from sinusoidal to relaxation oscillations is explained by the modification of the phase plane partitioning when the coupling capacitance is varying. The jumps of the describing point in the phase plane help to understand the difficulties occurring in simulation of multivibrators. Finally, the formula for calculation of frequency in relaxation oscillations is given. All results are verified in simulations.