Van der Pol Oscillator

This article describe about Van der Pol Oscillator, which is a single pentode tube and an external circuit with a capacitance that causes the device to switch between two values of the screen voltage. It  such as theory of average, successive approximations and symbolic dynamics. Van der Pol found stable oscillations, which he called relaxation-oscillations and are now known as limit cycles, in electrical circuits employing vacuum tubes. Van der Pol Equation has a long history of being used in both the physical and biological sciences.