Investigation of stochastic resonance (SR) near homoclinic bifurcation   in a unijunction transistor (UJT) relaxation oscillator
  A P-spice simulation followed by an experiment with a unijunction transistor (UJT) has been carried out to investigate stochastic resonance (SR) in which the response of a nonlinear system to a weak periodic input signal is amplified by an optimum level of noise. The experiments were carried out in the vicinity of homoclinic bifurcation and the quantification of SR has been done by normal variance (NV) and signal to noise ratio (SNR) techniques. We have also developed a tentative mathematical model based on the current-voltage characteristic of the UJT and obtained a second order differential equation that was solved using MATLAB to yield a response similar to the one observed experimentally. 
Souvik Bose, M.S. Janaki, Sandip Sarkar and A.N. Sekar Iyengar
nlin.AO