NFC
Generates a 13.56 MHz RF carrier across an antenna coil, modulates it for outgoing data, and demodulates back-modulation from a passive tag (or active peer) to exchange payloads at 106–424 kbit/s.
A class-C amplifier drives a tuned LC antenna at 13.56 MHz; a passive NFC tag's antenna couples inductively, harvesting power and load-modulating the carrier with its data. The reader's receiver demodulates this load modulation with an envelope detector. Three modes — card emulation (phone acts as a tag), reader/writer (phone reads tags), peer-to-peer (phone-to-phone) — share the same physical layer with different framing.
In plain terms
Like two tuning forks held together — when the reader hums at exactly 13.56 MHz, the nearby tag fork (the smart card) starts ringing, and any tap on it modulates the hum back as data.
Why designers use it
- Mobile payments — Apple Pay and Google Pay both use NFC card emulation to send tokenised credit-card data to retail terminals.
- Transit cards — billions of MIFARE/CIPURSE/Calypso tickets in Tokyo, London, NYC, and Paris are NFC.
- Tap-to-pair — pair a Bluetooth speaker by holding the phone to it; the NFC tag exchanges Bluetooth address and PIN.
- Smart product tags — pharma anti-counterfeit, museum exhibit info, business-card style sharing.
Best for
- Payments
- Access control
- Smart tags
Key specifications
- Operating limits: Check the exact manufacturer's datasheet (A family name does not establish voltage, current, temperature or timing limits.)
- Pin assignment: Match the complete part and package code (A similar name or function does not guarantee the same wiring.)
- Mechanical fit: Use the exact package drawing (Check pad layout, dimensions and viewing direction before building.)
When not to use it
- When the required operating distance or alignment tolerance is outside the chosen reader-and-tag system's specification.
- When the required throughput, protocol or data capacity is not supported by the selected devices.
Common mistakes
- Detuning the antenna — every metallic object near the loop changes the resonant frequency; recalibrate after assembly.
- Neglecting to load-balance — a small phone antenna near a metal phone frame can lose 50 % of read range without proper Q tuning.
Where you will find it
- An iPhone 15 Pro's Apple-designed N-series NFC controller (descended from NXP technology) handles Apple Pay transactions: the chip's secure-element binding means a Visa token never leaves the iPhone in plaintext when a user taps to pay at a Square terminal.
- A London Oyster card is an NXP MIFARE DESFire EV1 NFC tag whose smart-card chip is read by Cubic Transportation's TfL gate readers in 300 ms: the inductive link both powers the tag and exchanges the encrypted ride-balance update.
- A Tile Mate Bluetooth tracker uses an NXP NTAG216 NFC tag to encode its phone-number-back-to-owner URL: when a finder taps the lost tracker, the iOS NFC reader opens the contact-owner page without needing the Tile app installed.
A short history
The NFC Forum's Release 15 description distinguishes the certified operating volume from an informal maximum read-distance claim. It describes an increase from about 0.5 cm to up to 2 cm for compliant connections. These figures do not promise the same distance for every older device or antenna arrangement: NFC remains a close-proximity interaction.