  A nonlinear electronic circuit comprising of three nodes with a feedback loop
is analyzed. The system has two stable states, a uniform state and a sinusoidal
oscillating state, and it transitions from one to another by means of a Hopf
bifurcation. The stability of this system is analyzed with nonlinear equations
derived from a repressilator-like transistor circuit. The apparatus is simple
and inexpensive, and the experiment demonstrates aspects of nonlinear dynamical
systems in an advanced undergraduate laboratory setting.
