The series resonance circuit with a linear inductance and a ferroelectric capacitance has been used to realize a nonlinear dynamical system. As dielectric material in the capacitor we use triglycine sulfate, usually abbreviated TGS, which is one of the most thoroughly investigated ferroelectrics. Below the Curie temperatureTC= 49°CTGS has two possible states of polarization. The switching of domains under the influence of an external electric field higher than the coercive field from one state of polarization to the opposite one is a highly nonlinear process. If the series resonance circuit is driven by AC voltage of sufficiently high amplitude and suitably chosen frequencies different kinds of bifurcations up to chaotic behaviour can be observed. It is well known, that in the vicinity of a bifurcation the resonance circuit can act to amplify small periodic perturbations. In our system we have demonstrated this effect near a period doubling bifurcation by introducing the periodic perturbation as an amplitude modulation of the driving voltage.Now we present another kind of perturbation of the resonance circuit. Because TGS is a material with a very large pyroelectric effect we introduced the perturbation into the system by periodic infrared irradiation of the ferroelectric. The resulting periodic modulation of the temperature of the TGS‐crystal yields an electrical signal via the pyroelectric effect, which can be amplified near a period doubling bifurcation. Detailed investigations were performed to optimize this effect. The result may be considered as a new method of pyroelectric detection. © 2004 American Institute of Physics