A Semiconductor Current Limiter

The two-terminal constant-current device described herein employs the principles of the field effect transistor. Current flows parallel to a junction through a thin sheet of semiconductor. The reverse bias on the junction controls the effective thickness of the sheet and thereby controls its conductance. An extension of Shockley's step-junction-device theory is presented, as well as a formulation for the graded-junction case. Several structures are discussed and compared, and fabrication procedure for the presently used structure is outlined. The current limiter has been employed advantageously as an ac switch, a current regulator, for discrimination between ac and dc, and in simple circuits for sawtooth and step function generation and for digital-to-analog conversion.