Theoretical analysis of constructive and technological restrictions in the avalanche photodiode structure for photon-counting mode is made in this work. It is shown that critical parameters are load resistance and a time constant of a photodiode internal capacity recharge. For decreasing this time constant one needs size restriction of separate section of the photodiode and association of several such sections on a crystal together with registration schemes.

Keywords: Avalanche photodiode, Mode of the account of photons, Constructive-technological restrictions, Model of avalanche breakdown

In the present paper we propose a modified approximation of a silicon bipolar transistor, which takes into account the frequency relationship of electromagnetic signals propagation in the substrate. These modifications were implemented because the experimental investigations and crosstalk simulations in the metallization layers of a silicon substrate have showed that the commonly used approximations based on lumped elements are not able to describe properly the mutual influence of signals at gigahertz frequencies. It was shown that the proposed method is suitable for high-frequency analog circuits design and it is based on sparse distribution of circuit elements and additional shielding of high-frequency chains. The reproducibility and stability of the circuit’s parameters is achieved by secondary devices which are added for correction and stabilization.

Keywords: heterostructure bipolar transistors, silicon-germanium base layer, ionizing radiation, simulation of analog cells using substrate influence effect, analog cells parameters stabilization and correction.