New type bandgap reference for UHF RFID tag

A novel low-voltage, low-power current mode bandgap reference circuit for the passive UHF RFID tag is presented. The I_CTAT current is generated by V_BE of the BJT transistor. The I_CTAT current is generated by the MOSFET biased in the sub-threshold region, based on the theory that the I-V curve of the sub-threshold MOSFET shows an exponential relationship. The circuit is designed and implemented by TSMC 0.18μm CMOS technology. The biggest variation of V_ref of the reference is smaller than 1.75％. Test results show that the power of the circuit is 0.65μW, and that the minimum operating voltage is 0.829V. The active area of the circuit is about 0.04mm². As a result, the read sensitivity of the tag with the proposed bandgap reference circuit is -16dBm.