Littelfuse, Inc.
CURRENT LIMITING CIRCUIT ARRANGEMENT

Abstract:

A floating two-terminal unipolar current limiting circuit arrangement implemented with enhancement mode devices and bipolar devices with a unique voltage-current operation curve. This operation curve makes this device particularly advantageous to instrumentation systems that are intended to experience large voltage transients and long-term exposure to voltages that would normally damage measurement equipment. The present current limiting device is designed to have a large impedance value prior to a "turn-on" voltage, then quickly transitions to a low-impedance state. When the conducted current exceeds a setpoint or a high-voltage event occurs, the current limiting device further transitions to the "cutoff" region, which transition resumes the initial high-impedance state. In one embodiment the threshold current may be set with internal components, while a further embodiment allows the current setpoint to be set by external components. The current limiting device designs according to the present embodiments allow for series scaling and parallel scaling.