*4.1. Transient Behavior*

The transient performance of the output voltage, in both stages, is displayed in Figure 4. The first stage performs the full-wave rectification by converting the negative input voltages (*VIN*) into positive ones (*VNVC*). The voltage drop on this stage is around 1 mV, whereas the total voltage drop on the circuit is around 12 mV, which is possible due to the reduction of the internal resistance of the main pass transistor M5. The achieved voltage drop is crucial to enhance the output voltage across the load.

**Figure 4.** Simulated waveforms of the rectifier for RLOAD = 5.5 kΩ and CLOAD = 2 μF.

Figure 5 shows the VCE behavior versus the input voltage amplitude for different *RLOAD* values. It is possible to observe that the proposed rectifier can work efficiently for an input voltage range from 0.45 V to 1 V for different ohmic loads, with a VCE varying between 96% and 99%. For an input voltage lower than 0.4 V, the VCE sharply decreases because the NVC transistors will enter the subthreshold region or even cut-off. Moreover, it can be noticed that the rectifier VCE is higher for larger load resistors, as would be expected.

**Figure 5.** VCE versus input voltage amplitude simulated for different ohmic loads.

#### *4.2. Reverse Leakage Current Analysis*

The reverse leakage current analysis is one of the most important analyses to make in CMOS rectifiers because it affects the power efficiency of the overall system. This reverse leakage current is dependent on the delay of the comparator and, consequently, of the discharging path of the active diode provided by the AVC. Therefore, the analysis of the transient performance of the comparator is shown in Figure 6. It presents the output voltage of the comparator (*VCMP*), the input and output voltage of the active diode used to perform the comparison, the gate voltage of M5 (*VCAP*), and the current that flows through the active diode (*IM*5). As can be observed, the comparator immediately turns on the gate of the AVC transistor to create the discharge path when *VNVC* exceeds *Vrec*. At this stage, the current is flowing through M5, and *VCAP* is low, which leads to a low voltage drop because *VSG* is high. When *VNVC* drops below *Vrec*, the comparator then quickly turns off the AVC, and consequently the active diode. Thus, the proposed structure does not exhibit reverse leakage current that would degrade the PCE of the proposed rectifier.

**Figure 6.** Simulated comparator behavior in steady state for RLOAD = 500 Ω and CLOAD = 2 μF.
