Low power analog circuit design for RFID sensing circuits

This paper presents low power circuit design for voltage regulator and resistor to digital converter that are used in a RFID-like sensing circuit for measuring the resistance of a sol-gel sensor. The regulator circuit has simple circuit structure and consumes zero DC current (except the current drained by its load). The resistor to digital converter consists of a cascoded current mirror, a reference resistor and a charge-redistribution (CR) ADC circuit. The proposed circuit techniques reduce the size of the ADC capacitor array by half compared to traditional CR ADCs with the same resolution. The proposed techniques also significantly reduce the circuit power consumption with enhanced measurement accuracy. The proposed circuits and a RFID energy harvesting circuit for powering the proposed circuits are implemented using a 0.13µ CMOS technology. Circuit simulations are presented to examine the performance of the proposed circuits.