A differential threshold voltage compensated RF-DC power converter for RFID tag ICs

The usage of threshold voltage (Vth) compensation techniques allows to decrease the input quality factor of RF-DC power converters or more specifically RF charge pumps at low levels of input power, and thus enable the implementation of highly sensitive broadband UHF radiofrequency identification (RFID) transponders (tags). In this work, we present a Vth compensation approach using a combination of gate and bulk biasing for differential charge pump implementations. Prototypes of an eight stage RF charge pump using the proposed Vth compensation technique have been manufactured in a low power 40 nm CMOS technology. Measurements of the test circuits reveal a high power conversion efficiency of 42.7 % and a low input quality factor of approximately 14, at an output power of 4 μW and a DC voltage level of 1 V. Furthermore, we compare the obtained measurement results with two previously published RF charge pumps.