Two sets of experimental results are given to demonstrate how modern nonlinear dynamics can be used to understand the dynamics of extrinsic Ge photoconductors. In the first, we show how complex and apparently random chaotic broadband noise is physically produced in devices which have nearly ideal stochastic noise performance in the absence of drive. In the second, we demonstrate that the circle map, a simple model of periodically-driven active oscillators with universal predictions, quantitatively describes the dynamics of a driven spatially-dependent high field instability in Ge. © 1986 IOP Publishing Ltd.