Introduction. High voltage silicon mass transistors have the ability to perform circuit functions similar to the gas thyratron tube. Upon being triggered the transistor junction breaks down, or "avalanches", and can conduct a large current for a short time. The rise time of the avalanche breakdown pulse can be short, and the delay between triggering and avalanching can be short and very consistent. This avalanche action is non-destructive if the amount of peak and average power being dissipated at the junction is limited by the circuitry.