Which RF rectifier topology wins? It depends on the power.

When an antenna picks up an RF signal — from an RFID reader, a Wi‑Fi access point, or the ambient cellular bath — you have to decide what to do with the captured sinusoid. The obvious answer is “rectify it.” The harder question is how.

The textbook offers four reasonable choices: a single‑diode half‑wave rectifier, a Greinacher voltage doubler, a four‑diode full‑wave bridge, or a multi‑stage Cockcroft–Walton ladder. All four appear in real designs. They behave radically differently across the input‑power range — differently enough that it’s easy to reach for the wrong one if you reason about the topology alone and forget the operating regime.

So I built an interactive tool that puts all four side by side.

What you’re looking at: four real schematics with current paths animated per half‑cycle, plus an η-vs-P_in sweep that places a dot on each curve at the current operating point. Drag the P_in slider from −30 dBm (the microwatt RFID range) to +20 dBm (a healthy 100 mW) and watch the leader change.

Three observations worth internalizing:

• Below about −20 dBm, only the cascade and the doubler conduct at all. The bridge needs two diode drops of input — about 240 mV at V_D = 120 mV — before any current flows, and at 1 µW into a 50 Ω antenna, V_pk is only ~63 mV. The bridge is locked out.
• Above about +10 dBm, the cascade’s cumulative 2N·V_D losses dominate. The bridge wins on simplicity: only 2·V_D total, full‑wave operation, done.
• The half‑wave never wins, anywhere. Same V_D loss as the doubler, half the duty cycle. Drag the slider and try to find one operating point where it leads — there isn’t one. (It survives in practice only because the BoM is one diode.)

The crossover point depends quite sensitively on V_D. Drop it from 250 mV to 100 mV — the difference between a generic Schottky and an HSMS‑2850‑class part — and the doubler’s useful range extends about 8 dB downward. That alone often justifies the cost of low‑V_D parts in energy‑harvesting designs.

Every component, parameter, and formula has a tooltip — hover anything to see what it means and where the number comes from. Math is rendered through KaTeX. The toggle in the top‑right switches between English and Ukrainian.

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