Testing high-density neural recording devices and validating complex spike-sorting algorithms requires immediate and reliable access to functional cellular network signals. However, relying on live in vitro cultures is highly impractical due to prolonged maturation times, the inherent fragility of living tissue, and their unpredictable, non-deterministic behavior. To address these limitations, this thesis presents the design and development of a Spike Generator, a hardware-in-the-loop testbench engineered to accurately synthesize bio-realistic extracellular neural signals in the microvolt range. By providing full control over the generated waveforms, this platform enables a deterministic preliminary validation of recording instrumentation, allowing systems to be thoroughly verified before transitioning to biological assays.