An efficient CMOS rectifier with low-voltage operation for RFID tags

A high-efficiency CMOS rectifier for radio-frequency identification (RFID) applications is presented. Using an on-chip generated clock signal, a new switching scheme is proposed to enhance the power efficiency of the conventional 4 transistor (4T)-cell rectifier. By switching the gate of charge-transfer transistors to the intermediate nodes of preceding and succeeding stages, low on-resistance and small leakage current are obtained simultaneously. To further improve the low-voltage operation capability, an external gate-boosting technique is also applied to the proposed design which enables an efficient operation for input voltage levels well below the nominal standard threshold voltage of MOS transistors. The two proposed rectifier architectures are designed and laid out in a standard 0.13µm CMOS technology. For a 950 MHz RF input and 10 kΩ output load, post-layout simulation results confirm a power conversion efficiency (PCE) of 74% at −10 dBm and 57%at −26 dBm for switched 4T-cell and gate-boosted switched 4T-cell, respectively. While the PCE of the proposed switched 4T-cell rectifier compares favorably with that of the state-of-the-art rectifier designs, the gate-boosted version achieves a relatively high PCE while operating with a very low input power.