A Model for MOS Diodes With $V_{\rm th}$ Cancellation in RFID Rectifiers

A theoretical model for diode-connected MOS transistors with a threshold cancellation technique is developed. The model is based on a detailed analysis of the technique with internal threshold cancellation (ITC) and reveals design insight and performance limitations. Derived design equations illustrate the tradeoff between the voltage drop and the reverse leakage of the diode. Furthermore, a design procedure for the optimization of the power conversion efficiency (PCE) of a bridge rectifier with ITC MOS diodes was developed based on the model. A rectifier was designed and implemented in an austriamicrosystems 0.35-μm CMOS process, and Cadence simulation results of the PCE and the voltage conversion efficiency show good agreement with the model.