Neural networks composed of two or four cells with combined, electrical and inhibitory, synapses and realized for various network topologies were examined. The aim of this study was to determine a set of phases of oscillatory cycle in which different patterns of activity, characteristic for such networks, can be switched under an external stimulus. In particular, we studied susceptibility of switching between in-phase (IP) and anti-phase (AP) patterns (and vice versa). Our results demonstrate that windows of switching between patterns are similar for networks with electrical and mixed synapses and, in general, relatively independent of the network topology. The only effect of the network topology is an increase of the robustness of the AP pattern in networks of ring-like connectivity. The switching window width and thereby the robustness of the transitions between patterns decreases with the increase of the electrical coupling strength.
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A novel square wave generator (relaxation oscillator) with controllable frequency is described. It employs two universal current conveyors (UCC) and grounded passive elements. The generator includes integrator with two integration capacitors that alternate in charging which results in linear and precise control of frequency by voltage. New implementation of UCC with attractive properties in CMOS 0.18 μm technology is also presented. Computer simulations in PSpice environment confirm the theoretical assumptions.
PL
W artykule przedstawiono nowy generator fali prostokątnej o regulowanej częstotliwości, zbudowany na bazie dwóch przekaźników prądowych (UCC) oraz elementów pasywnych. Opisano także zastosowanie technologii CMOS 0,18um do przekaźników. Dokonano weryfikacji symulacyjnej w programie PSpice.
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