Active Device

What Is an Active Device?

An active NFC device has its own power source (battery, USB, or mains) and can independently generate a 13.56 MHz RF field to initiate NFC communication. Unlike passive tags that rely on harvested energy, active devices power their own NFC controller and antenna driver circuits.

Types of Active NFC Devices

NFC Operating Modes

Active devices can operate in all three modes defined by the NFC Forum:

1. Reader/Writer Mode: The device generates an RF field and communicates with a passive tag. Most common mode for scanning tags.
2. Card Emulation Mode: The device acts as a passive card. A separate reader generates the field. Powers mobile payments (Apple Pay, Google Pay).
3. Peer-to-Peer Mode: Two active devices alternate generating the RF field to exchange data bidirectionally using LLCP.

Active-Active vs Active-Passive

• Active-Passive: A smartphone (active) reads an NFC sticker (passive). The smartphone generates the field; the tag harvests energy and responds via load modulation.
• Active-Active: Two smartphones exchange data, alternating who generates the RF field.

Pure passive-to-passive communication is physically impossible — at least one device must generate the electromagnetic field.

NFC Controller

Every active deviceactive devicePowered NFC device that generates its own RF fieldView full → contains an NFC controller IC managing the protocol stack: RF field generation, protocol negotiation (NFC-A, NFC-B, NFC-F), anti-collision, NDEF parsing, and secure element communication.

Power Consumption

NFC is designed for minimal power impact. In low-power polling mode, the controller periodically checks for tags at 100-500 ms intervals. Active communication draws 50-150 mA for 100-500 ms per interaction — negligible impact on battery life.