Level-shift Circuit using Subthreshold-operated CMOS Operational Amplifiers

A CMOS level shifter that operates as a dc-cut capacitor is proposed. This circuit consists of a differential pair and a unity-gain buffer connected to one input of the differential pair. The unity-gain buffer consists of a subthreshold-operated operational amplifier and operates very slowly. The circuit operates as a high-pass filter and transmits ac signals but cuts off a dc voltage level. Therefore it can be used to connect two analog circuits having different dc levels. The results for the simulation and fabrication of this level shifter circuit are described.