Solid-state log n-period System

A log n-period system with all solid-state components has been designed and tested. The logarithmic converter uses the logarithmic transfer relationship between the short-circuit collector current and the base-emitter voltage of a silicon transistor to convert an exponentially varying ion chamber current to a linear voltage. The operational amplifier in the logarithmic converter has a junction-type field-effect transistor at its input for very high input impedance. To obtain the reactor period, the linear voltage is differentiated by a circuit whose damping is controlled by the level and rate of change of its input. This circuit adequately protects a nuclear reactor during startup. The overall system is accurate, reliable and stable.