Switching time in relaxation oscillations of emitter-coupled multivibrators

This paper gives an estimation of the switching time between ON and OFF transistor states for the emitter-coupled multivibrator. The calculation uses the root locus of the characteristic equation for the oscillator small-signal equivalent circuit, while changing the device current as a parameter. The switching time is found using a fitting location of the root in the right half of the s-plane. The oscillation frequency is also obtained. The approach provides a further insight into switching behavior of relaxation oscillators, gives an accurate estimation of the oscillation frequency, and allows one to establish a useful connection between sinusoidal and relaxation oscillators. The theoretical results are confirmed by simulations.