Hysteresis based neural oscillators for VLSI implementations

The actual tendency in most of the work that is being done in VLSI neural network research is to use the simplest possible models to perform the desired tasks. This yields to the use of sigmoidal type neurons that have a static input-output relationship. However, in some cases, especially when the research is close to biological neuron systems emulation, such simplifled models are not always valid. In these cases, a neuron model closer to biological neurons is needed, namely the oscillatory neuron [l-41. For these neurons, when they are active, their output is a sequence of pulses. In this paper we present several circuits that can be set in an active state to yield an oscillatory output. The difference between the circuits is based on whether the output has two unique output states (off, or on flring at a specific frequency), or has a continuum between the on and off states so t h a t the output frequency changes sigmoidally between zero and its maximum.