Sinusoidal and relaxation oscillations in emitter-coupled multivibrators

The paper investigates transition from sinusoidal to relaxation oscillations in emitter-coupled multivibrator. First, the differential equation for sinusoidal regime is obtained, and the frequency and amplitude are calculated. Then, the transition from sinusoidal to relaxation oscillations is traced using the phase plane of this equation. The transition is explained by modification of the shape of central branch for the isocline of horizontal tangents. Finally, the sinusoidal regime approximation for static impedance seen by the coupling capacitor is used to calculate the oscillation period in relaxation oscillation. The results were verified in simulations.