Ultra low-voltage switched current mirror

Abstract

In this paper we present a continuous time ultra low voltage current mirror based on clocked semi-floating-gate transistors used in low-voltage digital CMOS circuits. By imposing offsets to semi-floating-gate nodes the current level may be increased while maintaining a very low supply voltage. The offset voltages are used to shift the effective threshold voltage of the evaluating transistors. The proposed current mirror can operate at supply voltages below 250mV and in continuous time. The current mirror performs an auto zero (chopper) function. The simulated data presented are obtained using the Spectre simulator provided by Cadence and valid for a 90nm CMOS process. We have included an ultra low voltage current mirror with adjustable current levels.